Sensor-equipped bearing for wheel

ABSTRACT

To provide a sensor equipped wheel support bearing assembly, in which a load sensor can be installed compactly in an automotive vehicle, maintaining a high sensitivity while damage and/or malfunction caused by the external environments and/or the electromagnetic noises are avoided, with low manufacturing cost. This bearing assembly includes outer and inner members having respective rolling surfaces and a plurality of rows of rolling elements interposed between those rolling surfaces. A strain sensor unit including a sensor element is fitted to one of the outer and inner members, which is a stationary member, for example, the outer member. A sensor mounting surface of the strain sensor unit fitted with the sensor element has a covering member made of a resin, which is over-molded, or an elastomer bonded by vulcanization, so as to cover the sensor element sealingly.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is based on and claims priority to Japanese patentapplication No. 2007-080558, filed Mar. 27, 2007, Japanese patentapplication No. 2007-093779, filed Mar. 30, 2007, Japanese patentapplication No. 2007-178356, filed Jul. 6, 2007, Japanese patentapplication No. 2007-182780, filed Jul. 12, 2007, and Japanese patentapplication No. 2007-190358, filed Jul. 23, 2007, the disclosures ofwhich are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a sensor equipped wheel support bearingassembly having a load sensor built therein for detecting a load imposedon a bearing unit for a vehicle wheel.

2. Description of the Related Art

For safety travel of an automotive vehicle, the wheel support bearingassembly has been well known, in which sensors for detecting therespective rotation speeds of the vehicle wheels are employed. While theautomobile traveling safety precaution is generally taken by detectingthe rotational speed of the respective vehicle wheel in variouslocations, it is not sufficient with only the rotational speed of thevehicle wheel and, therefore, it is desired to achieve a control forsafety purpose with the use of other sensor signals.

In view of the above, it may be contemplated to achieve the vehiclestability control based on a load acting on each of the vehicle wheelsduring travel of an automotive vehicle. By way of example, a large loadacts on the outside wheels during the cornering, on the wheels on oneside during the run along horizontally inclined road surfaces or on thefront wheels during the braking, and, thus, uneven load acts on thevehicle wheels. Also, even in the case of the uneven live load, theloads acting on those wheels tend to become uneven. For this reason, ifthe loads acting on the wheels can be detected as needed, suspensionsystems for the vehicle wheels can be controlled beforehand based onresults of detection of the loads so that the stability control of theautomotive vehicle during the traveling thereof (for example, preventionof a rolling motion during the cornering, prevention of diving of thefront wheels during the braking, and prevention of diving of the vehiclewheels brought about by an uneven distribution of live loads) can beaccomplished. However, it is difficult to find a suitable space forinstallation of the load sensor for detecting the load acting on therespective vehicle wheel and, therefore, the stability control throughthe detection of the load is hardly realized.

Also, in the event in the near future the steer-by-wire is introducedand the system in which the wheel axle and the steering come not to becoupled mechanically with each other is increasingly used, transmissionof information on the road surface to the steering wheel, then hold by adriver, by detecting a wheel axis direction load would come to berequired.

In order to meet those needs hitherto recognized, a wheel supportbearing assembly has been suggested, in which a strain gauge is affixedto an outer ring of the wheel support bearing assembly so that strainsoccurring in the outer ring can be detected when the rolling elementspass through. (See, for example, the Patent Documents 1 listed below.)Also, the wheel support bearing assembly has been suggested, in which asensor device including not a strain gauge attached directly to an outerring, but a load sensor for detecting strains attached to a sensorsupport member. (See, for example, the Patent Document 2 listed below.)In the case of the Patent Document 2 referred to, the sensor supportmember is made up of a horizontal portion, held in engagement with anouter peripheral surface of an outer ring, and a vertical portion heldin engagement with a vehicle body fitting flange of the outer ring, withthe load sensor attached to the horizontal portion.

[Patent Document 1] Japanese Laid-open Patent Publication No.2003-530565 [Patent Document 2] Japanese Laid-open Patent PublicationNo. 2006-077807 [Patent Document 3] JP Patent Application No.2006-062252 [Patent Document 4] JP Patent Application No. 2006-228906SUMMARY OF THE INVENTION

The outer ring of the wheel support bearing assembly is a bearingcomponent part having a rolling surface defined therein and required tohave a strength, which bearing component part is manufactured throughcomplicated process steps including, for example, a plastic forming, aturning process, a heat treatment and a grinding process, and,accordingly, while a strain gauge is attached to the outer ring such asdisclosed in the Patent Document 1 referred to above, there is a problemin that the productivity is low and the cost of manufacturing thereofduring a mass production tends to become high. Also, it is not easy todetect a strain occurring in the outer ring with high sensitivity and,when a result of such detection is utilized in controlling the vehiclestability of an automotive vehicle then travelling, a problem will arisein association with the accuracy of the control. There is also such aproblem that since a portion of the wheel support bearing assembly isprocessed, the bearing rigidity tends to be lowered.

When arrangement is made to fit the sensor device, including a sensorsupport member and a load sensor fitted to the sensor support member forthe detection of strains, to the outer ring such as disclosed in thePatent Document 2 referred to above, not only can the load sensor beinstalled easily, but also the productivity can be increased and, whenthe position at which the sensor support member is fixed to the outerring is properly set, the strains occurring in the outer member can bedetected with a high sensitivity. However, in order for the strains inthe outer ring to be detected with a high sensitivity, it is necessaryto fix the sensor support member to the outer ring at two or morelocations spaced from each other. For this reason, the shape of thesensor support member tends to become complicated, making it difficultto fix the sensor support member to the outer ring in a stabilizedposture. In particular, where the sensor support member is to be fixedto a peripheral surface of the outer ring which has a cylindricalsurface shape, rattling tends to occur between respective contactsurfaces of the sensor support member and the outer ring and, therefore,the posture in which the sensor support member is fixed is apt to becomeinstable. When the posture of fixing the sensor support member isinstable, the strains occurring in the outer ring will not be properlytransferred to the sensor support member, failing to detect the strainsin the outer ring with a high precision.

In view of the foregoing, the applicant, to which the present inventionhas been assigned, has suggested fixing of a strain generating memberand a strain sensor unit to the outer ring through a fixing member suchas, for example, a spacer (in the Patent Documents 3 and 4 listedabove). In such case, there is the possibility that displacement inposition of the fixing member referred to above may result in anundesirable movement of the fulcrum about which the sensor deforms,resulting in an increased variation in sensor strain sensitivity.

In order to alleviate those problems, it may be contemplated to fit astrain sensor unit, made up of a strain generating member and a sensorelement such as, for example, a strain gauge fitted to the straingenerating member for detecting strains occurring in the straingenerating member, to, for example, the outer ring which is a stationaryring of a wheel support bearing assembly. In such case, the straingenerating member is rendered to have a first contact fixing element,which is fixed to a surface of a vehicle body fitting flange in theouter ring, and a second contact fixing element fixed to an outerperiphery of the outer ring.

In the wheel support bearing assembly of the structure described above,when a load acts on a hub unit, which is a rotating member, during thetravel of an automotive vehicle, the outer member undergoes adeformation through rolling elements and such deformation is transferredto the strain generating member of the strain sensor unit so that thesensor element, fitted to the strain generating member, may measure thestrains. Since the first contact fixing element of the strain generatingmember is fixed to the surface of the vehicle body fitting flange in theouter ring while the second contact fixing element is fixed to the outerring outer periphery, respective positions of the first and secondcontact fixing elements in a radial direction are different from eachother and the strains occurring in the outer ring can appear as expandedin the strain generating member. Since the sensor element measures theexpanded strains, the strains occurring in the outer ring can bedetected with a high sensitivity.

In the construction described above, however, since the strain sensorunit is exposed to the outside of the wheel support bearing assembly,there is the possibility that due to external environments (ingress ofmuddy water and/or collision with foreign matter), the strain sensorunit may be damaged or malfunctioned and, therefore, it would not bepossible to achieve an accurate strain detection for a long time. Also,since the sensor element employed in the strain sensor unit is anelectronic component part, it tends to be affected by electromagneticnoises from the outside and, therefore, the reliability of a result ofdetection will be lowered if the sensor element is exposed to theoutside as hereinabove described.

An object of the present invention is to provide a sensor equipped wheelsupport bearing assembly, in which a sensor for the detection of theload can be installed in an automotive vehicle in a stabilized postureand compactly, which can detect the load, acting on a vehicle wheel, fora long time with a high sensitivity while any possible damage and/ormalfunction caused by the external environments and/or influence broughtabout by the electromagnetic noises are avoided, and which is low incost during the mass production, is effective to avoid an undesirablemovement of the fulcrum, about which the sensor deforms, and effectiveto reduce variation in sensor strain sensitivity.

The sensor equipped wheel support bearing assembly in accordance withone embodiment of the present invention is a wheel support bearingassembly for supporting a vehicle wheel rotatably relative to a vehiclebody, including an outer member having an inner periphery formed with aplurality of rolling surfaces; an inner member having rolling surfacesdefined therein in face-to-face relation with the respective rollingsurfaces in the outer member; a plurality of rows of rolling elementsinterposed between those rolling surfaces; a strain sensor unit, made upof a strain generating member and a sensor element fitted to the straingenerating member for detecting strains induced in the strain generatingmember, is fitted to one of the outer and inner members, that serves asa stationary member; and a covering member that covers at least thesensor element sealingly, provided on a mounting surface of the straingenerating member of the strain sensor unit, on which the sensor elementis mounted, the covering member being made of a resin, which isover-molded, or an elastomer bonded by vulcanization.

When a load acts on the rotating member incident to travel of theautomotive vehicle, the stationary member undergoes deformation throughthe rolling elements, which deformation in turn result in a strainbrought about on the strain generating member. The strain element fittedto the strain generating member detects the strain induced in the straingenerating member. By determining the relation between the strain andthe load beforehand by means of a series of experiments and/orsimulations, the load acting on the vehicle wheel can be detected froman output of the sensor element. The load so detected is processed bythe sensor signal processing circuit and is then used in vehicle controlof the automotive vehicle.

The wheel support bearing assembly of the structure described above isso designed that the strain sensor unit including the strain generatingmember and the sensor element fitted to the strain generating member isfitted to the stationary member and, therefore, the sensor for thedetection of the load can be installed compactly. Also, since the straingenerating member is a simple component part that is fitted to thestationary member, fitting of the sensor element thereto makes itpossible to render it to be excellent in mass productivity and tofacilitate reduction in cost.

In particular, since the covering member made of an over-molded resin oran elastomer bonded by vulcanization is provided in the mounting surfaceof the strain generating member where the sensor element is fitted, tothereby the sensor element to be covered sealingly with this coveringmember, it is possible to avoid an undesirable damage or malfunction ofthe sensor element, which would otherwise result from intrusion of muddywater and/or collision with foreign matter depending on the externalenvironment. As a result thereof, a highly precise strain detection canbe achieved for a long time. It is also possible to prevent influencesof the electromagnetic noises, brought about from the outside, frombeing extended to the sensor element and, therefore, a highly precisestrain measurement can be accomplished.

The strain generating member referred to above may have first and secondcontact fixing elements fixed to respective locations of the stationarymember, in which the first contact fixing element is fixed to a flangesurface provided in the stationary member and the second contact fixingelement is fixed to a peripheral surface of the stationary member.

While hereinabove described the strain generating member has the contactfixing element at two locations, in which the first contact fixingelement is the flange surface provided in the stationary member and thesecond contact fixing element is the peripheral surface of thestationary member, respective positions of the first and second contactfixing elements in a radial direction differ from each other and thestrains occurring in the stationary member can be caused to appear astransferred and expanded in the strain generating member. Since thesensor element measures the strains so transferred and expanded, thestrain occurring in the stationary member can be detected with a highsensitivity and the accuracy of measurement of the load can beincreased.

In one embodiment of the present invention, the sensor element in thestrain sensor unit may be provided with a cable drawn outwardly from alocation proximate to the second contact fixing element in the straingenerating member fixed to the peripheral surface of the stationarymember in a direction circumferentially of the stationary member.

In such case, since the cable for the sensor element can be wired alongthe peripheral surface of the stationary member, the cable will notdisturb as compared with the wiring thereof along the flange of thestationary member, and, therefore, influences of the electromagneticnoises on an output signal of the sensor element can be reduced further.

While hereinabove described the cable for the sensor element in thestrain sensor unit is drawn outwardly from the location proximate to thecontact fixing element of the strain generating member relative to theperipheral surface of the stationary member in the peripheral directionof the stationary member, the cable may be fixed to the peripheralsurface of the stationary member by means of a clamp member equippedwith a ferrite.

In the case of this construction, since the cable is fixed to theperipheral surface of the stationary member by the use of the clampmember provided with a ferrite core, the resistance to noises appearingin a signal path from the sensor element to a signal processing circuitcan be increased. Also, addition of the ferrite core, having a functionof effectively attenuating a high frequency component such as theelectromagnetic noises, to the clamp member is effective to eliminatethe need of an extra space for installation of the ferrite core and,also, to facilitate fixing of the ferrite core.

The use may be made of an acting force calculating section operable inresponse to an output from the sensor element to calculate an externalforce acting on the wheel support bearing assembly or a force actingbetween a tire and a road surface.

When the external force, which is obtained from the acting forcecalculating section and which acts on the wheel support bearing assemblyor the working force, which is obtained from the acting forcecalculating section and which is developed between the tire and the roadsurface, is used in a vehicle control of the automotive vehicle, ameticulous vehicle control can be achieved.

In one embodiment of the present invention, the strain generating membermay of an L-shaped configuration including a radially oriented segment,extending in a radial direction, and an axially oriented segmentextending in an axial direction. In such case, strains tend toconcentrate in the vicinity of a corner on the side of the radiallyoriented segment, which lie between the radially oriented segment andthe axially oriented segment, and, therefore, a larger strain than thatin the outer member appears. Since the strains, which appears in theform of this large strain, can be measured, the strain occurring in theouter member can be detected with a high sensitivity and the strainmeasuring accuracy can be increased.

In one embodiment of the present invention, the strain generating memberof the strain sensor unit may include two or more fixing faces adaptedto be fixed to respective locations of the outer member spaced from eachother, and contact fixing elements each interposed between each of thefixing faces and a fixing target surface to which the strain sensor unitis to be fixed, in which the contact fixing element is in the form of aspacer member having opposite end faces, one end face oriented towardsthe fixing face having a shape conforming with that of the fixing faceand the other end face oriented towards the fixing target surface havinga shape conforming with that of the fixing target surface.

When the stationary member undergoes deformation, the outer memberdeforms regardless of whether the outer member is the rotating member orwhether the outer member is the stationary member. Deformation of theouter member brings about a strain on the strain generating memberthrough the spacer member. The strain generating member is fixed at thefixing faces at least the two locations spaced a distance from eachother relative to the outer member and since two or more deformations ofdifferent degrees are transferred from the outer member, the straingenerating member deforms considerably depending on the differencebetween those deformations.

Since between each of the fixing faces and the fixing target surfacewhere the strain sensor unit is to be fixed, the contact fixing element,which is a spacer member and which has an end face oriented towards theside of the fixing face, which end face is of the same shape as that ofthe fixing face, and also has an end face oriented towards the side ofthe fixing target surface, which end face is of the same shape as thatof the fixing target surface, is interposed, the strain generatingmember can be fixed to the outer member in a stabilized posture. Forthis reason, the strain occurring in the outer member is accuratelytransferred to the strain generating member and, hence, the strainoccurring in the outer member can be detected with a high precision.

Since the wheel support bearing assembly is such that the strain sensorunit made up of the strain generating member and the sensor elementfitted to this strain generating member is fixed to the outer memberthrough the spacer member, the sensor for the detection of the load canbe installed compactly in the automotive vehicle. Interposition of thespacer member between the strain generating member and the outer membermakes it possible to form the strain generating member in a simplifiedshape. When the sensor element is fitted to the strain generating memberof the simplified shape, it is possible to render the mass productivityto be excellent and the cost can be reduced. Also, since it is possibleto minimize the processing of the wheel support bearing assembly, thebearing rigidity will not be lowered.

At least one of the two or more spacer members referred to above may beso designed that the end face oriented towards the fixing face is in theform of a flat face and the end face oriented towards the fixing targetsurface is in the form of a cylindrical surface.

If the end face of the spacer member oriented towards the side of thefixing face is a flat face, the fixing face of the strain generatingmember can have a flat face and the strain generating member can besimplified in shape. Also, if the end face of the spacer member orientedtowards the fixing target surface is a cylindrical surface, the spacermember can be brought into tight contact with the outer peripheralsurface of the outer member and, therefore, the posture in which thestrain generating member is fixed can be stabilized.

In one embodiment of the present invention, one of the outer and innermembers, which serves as the stationary member, may be formed integrallywith a sensor fixing boss, and the strain generating member and at leastone strain sensor unit fitted to the strain generating member may beprovided in the stationary member through the sensor fixing boss.

Since the wheel support bearing assembly is so designed that since thestrain generating member and the strain sensor unit fitted to thisstrain generating member are so constructed as to be fitted to thestationary member, the sensor for the load detection can be installedcompactly in the automotive vehicle. Since the strain generating memberis a simple component parts that is fitted to one of the outer and innermembers serving as the stationary member, fitting of the strain sensorunit to the strain generating member is effective to provide anexcellent mass productivity and to reduce the cost.

Also, since the strain sensor unit is provided in the stationary memberthrough the sensor fixing boss formed in the stationary member, thefollowing functions and effects can be exhibited. The sensor fixing bosswill no longer displace in position relative to a stationary memberbody. Accordingly, it is possible to assuredly avoid an undesirablemovement of the sensor deforming fulcrum and, therefore, variation insensor strain sensitivity can be reduced.

The sensor fixing boss referred to above may have a first boss formedintegrally with the flange surface provided in the stationary member anda second boss formed integrally with the peripheral surface of thestationary member, in which the strain generating member includes afirst contact fixing element adapted to be fixed to a foremost end faceof the first boss in contact therewith and a second contact fixingelement adapted to be fixed to a foremost end face of the second boss incontact therewith.

In this case, since the first contact fixing element is held in contactwith the foremost end face of the first boss formed integrally with theflange surface of the stationary member and the second contact fixingelement is held in contact with the foremost end face of the second bossformed integrally with the peripheral surface of the stationary member,and if the first and second bosses have their protruding lengths thatare about equal to each other, the respective radial positions of thefirst and second contact fixing elements are different from each other.Accordingly, the strain in the stationary member is transferred to thestrain generating member and then appears as expanded. Since thetransferred and expanded strain is measured by the strain sensor unit,the strain occurring in the stationary member can be detected with ahigh sensitivity and the load measuring accuracy can be increased.

BRIEF DESCRIPTION OF THE DRAWINGS

In any event, the present invention will become more clearly understoodfrom the following description of preferred embodiments thereof, whentaken in conjunction with the accompanying drawings. However, theembodiments and the drawings are given only for the purpose ofillustration and explanation, and are not to be taken as limiting thescope of the present invention in any way whatsoever, which scope is tobe determined by the appended claims. In the accompanying drawings, likereference numerals are used to denote like parts throughout the severalviews, and:

FIG. 1 is a sectional view of a wheel support bearing assembly accordingto a first embodiment of the present invention;

FIG. 2 is a front elevational view showing an outer member of the wheelsupport bearing assembly as viewed from an outboard side;

FIG. 3 is an enlarged sectional view showing a mounting structure of astrain sensor unit in the wheel support bearing assembly;

FIG. 4 is a perspective view showing a modified form of a cable wiringstructure employed in the wheel support bearing assembly;

FIGS. 5A and 5B are perspective view showing different examples of aclamping member, respectively;

FIG. 6 is a diagram showing a sectional view of the wheel supportbearing assembly according to a second embodiment of the presentinvention, shown together with a block diagram of a conceptualconstruction of a detecting system therefor;

FIG. 7 is a front elevational view showing the outer member and thestrain sensor unit employed in the sensor equipped wheel support bearingassembly;

FIG. 8 is a broken side view showing the strain sensor unit separatedrelative to first and second bosses of the outer member;

FIG. 9 is a broken sectional view showing the strain sensor unit fixedto the first and second bosses of the outer member;

FIG. 10 is a front elevational view showing the outer member and thestrain sensor unit in a different sensor equipped wheel support bearingassembly;

FIG. 11 is a front elevational view showing the outer member and thestrain sensor unit employed in the sensor equipped wheel support bearingassembly;

FIG. 12 is a diagram showing a sectional view of the sensor equippedwheel support bearing assembly according to a first applied example,shown together with a block diagram of a conceptual construction of thedetecting system;

FIG. 13 is a fragmentary enlarged diagram of FIG. 12;

FIG. 14 is a front elevational view showing the outer member and thestrain sensor unit employed in the sensor equipped wheel support bearingassembly;

FIG. 15A is a broken front elevational view showing the strain sensorunit and first and second spacer members shown as separated from eachother;

FIG. 15B is a broken side view thereof;

FIG. 16 is a diagram showing a sectional structure of a sensor element;

FIG. 17 is a front elevational view showing the outer member and thestrain sensor unit employed in a different sensor equipped wheel supportbearing assembly;

FIG. 18 is a diagram showing a sectional view of the sensor equippedwheel support bearing assembly according to a second applied example,shown together with a block diagram of a conceptual construction of thedetecting system;

FIG. 19 is a front elevational view showing the outer member and thestrain sensor unit employed in the sensor equipped wheel support bearingassembly;

FIG. 20A is a front elevational view showing the strain sensor unit andthe first and second spacer members shown as separated from each other;

FIG. 20B is a bottom plan view showing the strain sensor unit and thefirst and second spacer members connected with each other;

FIG. 21 is a sectional view showing the sensor equipped wheel supportbearing assembly according to a suggested example;

FIG. 22 is a diagram showing a sectional view of the sensor equippedwheel support bearing assembly according to a third applied example,shown together with a block diagram of the conceptual construction ofthe detecting system;

FIG. 23 is a fragmentary enlarged sectional view showing the sensorequipped wheel support bearing assembly;

FIG. 24 is a front elevational view showing the outer member and thestrain sensor unit employed in the sensor equipped wheel support bearingassembly;

FIG. 25A is a rear view showing the strain sensor unit and first andsecond fitting members shown as separated from each other;

FIG. 25B is a broken side view thereof;

FIG. 26 is a fragmentary sectional view showing a different sensorequipped wheel support bearing assembly;

FIG. 27 is a fragmentary sectional view showing a further differentsensor equipped wheel support bearing assembly;

FIG. 28 is a fragmentary sectional view showing a yet further differentsensor equipped wheel support bearing assembly;

FIG. 29 is a diagram showing a sectional view of the sensor equippedwheel support bearing assembly according to a fourth applied example,shown together with a block diagram of the conceptual construction ofthe detecting system;

FIG. 30 is a broken sectional view showing an important portion of thesensor equipped wheel support bearing assembly on an enlarged scale;

FIG. 31 is a broken front elevational view showing the outer member andthe strain sensor unit employed in the sensor equipped wheel supportbearing assembly;

FIG. 32A is a rear view showing the strain sensor unit and the first andsecond fitting members shown as separated from each other;

FIG. 32B is a broken side view thereof, and

FIG. 33 is a front elevational view showing the outer member and thestrain sensor unit employed in the sensor equipped wheel support bearingassembly according to a fifth example.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A first embodiment of the present invention will now be described indetail with particular reference to FIGS. 1 to 3. This first embodimentis applied to a third generation model of a wheel support bearingassembly of an inner ring rotating type that is used for the support ofa vehicle drive wheel. It is to be noted that in the followingdescription, terms “outboard” and “inboard” represent one side of thevehicle body away from the longitudinal center of the vehicle body andthe other side of the vehicle body close to the longitudinal center ofthe vehicle body, respectively, when assembled in the vehicle body,respectively.

The sensor equipped wheel support bearing assembly according to thisembodiment includes, as shown in FIG. 1 in a sectional view, an outermember 1 having an inner periphery formed with a plurality of rollingsurfaces 3, an inner member 2 formed with rolling surfaces 4 opposed tothe respective rolling surfaces 3, and a plurality of rows of rollingelements 5 interposed between the rolling surfaces 3 of the outer member1 and the rolling surfaces 4 of the inner member 2. This wheel supportbearing assembly is rendered to be a double row angular contact ballbearing type, in which the rolling elements 5 are employed in the formof balls that are rollingly retained by a retainer 6 employed for eachrow. The rolling surfaces 3 and 4 have an arcuately sectioned shape andthe rolling surfaces 3 and 4 are so formed as to have respective contactangles held in back-to-back relation with each other. Opposite annularopen ends of a bearing space delimited between the outer member 1 andthe inner member 2 are sealed by respective sealing devices 7 and 8.

The outer member 1 serves as a stationary member and is of one-piececonstruction in its entirety including a flange 1 a formed in an outerperiphery thereof and adapted to be secured to a knuckle with asuspension system (not shown) for the automotive body structure. Theflange 1 a has a plurality of bolt holes 14 for fitting to a vehiclebody defined therein at a corresponding number of peripheral portionsthereof.

The inner member 2 serves as a rotating member and is made up of a hubunit 9 having a hub flange 9 a for the support of a vehicle wheel, andan inner ring 10 mounted on an inboard end of a cylindrical portion 9 bof the hub unit 9. The rolling surfaces 4 referred to previously areformed respectively in the hub unit 9 and the inner ring 10. The inboardend of the hub unit 9 has its outer periphery radially inwardly steppedto define an inner ring mounting area 12 of a reduced diameter, with theinner ring 10 fixedly mounted on such inner ring mounting area 12. Thehub unit 9 has a center bore 11 defined therein so as to extendcompletely through the length of the hub unit 9. The hub flange 9 a hasa plurality of press-fitting holes 15 defined in respectivecircumferential locations thereof for receiving the corresponding hubbolts BT that are press-fitted therein. The hub flange 9 a of the hubunit 9 has a root portion thereof formed with a cylindrical pilotportion 13 so as to protrude in an outboard direction, which pilotportion 13 serves to guide the vehicle wheel and brake components (notshown).

The outer member 1 has an outer peripheral portion mounted with a strainsensor unit 21 shown in FIG. 3. This strain sensor unit 21 is of a typeincluding a strain generating member 22, on which a sensor element 23for detecting a strain induced in such strain generating member 22 ismounted. The strain generating member 22 includes a first contact fixingelement 22 a adapted to be fixed to a portion in the vicinity of a bolthole 14 defined in an outboard oriented flange surface 1 aa of thevehicle body fitting flange 1 a in the outer member 1 in contacttherewith, and a second contact fixing element 22 b adapted to be fixedto an outer peripheral surface 1 b of the outer member 1 in contacttherewith. The first contact fixing element 22 a is fitted to a mountingrecess 83 formed in the flange surface 1 aa, but may be fitted to theflange surface 1 aa directly in contact therewith no mounting recess 83formed therein. The strain generating member 22 is of an L-shapedconfiguration having a radially oriented portion 22 c, extending in aradial direction and provided with the first contact fixing element 22a, and an axially oriented portion 22 d extending in an axial directionand provided with the second contact fixing element 22 b. Anintermediate area of the radially oriented portion 22 c is provided withthe first contact fixing element 22 a while a foremost end portion ofthe axially oriented portion 22 d is provided with the second contactfixing element 22 b. In the illustrated embodiment, the radiallyoriented portion 22 c and the axially oriented portion 22 d of thestrain generating member 22 are in the form of one piece component,while the first and second contact fixing elements 22 a and 22 b are inthe form of separate members from the one piece component, which arefixed to such one piece component. However, the strain generating member22 as a whole may be of one piece construction.

The sensor element 23 is arranged at a location radially inwardly of thefirst contact fixing element 22 a on a sensor mounting surface 22 ca,which is an inboard side surface of the radially oriented portion 22 cof the strain generating member 22. This sensor element 23 is fixed inposition to the radially oriented portion 22 c by a deposit of, forexample, a bonding agent. The radially oriented portion 22 c, where thesensor element 23 is arranged, is preferably reduced in wall thicknessto reduce the rigidity thereof as compared with that of the axiallyoriented portion 22 d.

The strain generating member 22 is provided with a covering member 24that covers at least the sensor element 23 in a sealing fashion, whichmember 22 extends from the sensor mounting surface 22 ca thereof to asurface 22 da of the axially oriented portion 22 d thereof that isopposed to the outer peripheral surface 1 b of the outer member 1. It isto be noted that the covering member 24 may be of a type capable ofcovering the entire surface of the strain generating member 22. Thiscovering member 24 is made of a resinous material that is over-molded onthat surface region discussed above or made of an elastomer (NBR, H-NBR,acrylic resin and so on) that is bonded by vulcanization. Theover-molded resinous material may be suitably employed in the form ofany one of the following materials:

Resins of the polyamide system: 66 Nylon, PPA (polyphthalamide) or thelike.

Synthetic resin of the special ether system: PPS or the like.

The above listed materials added with glass fibers.

The strain sensor unit 21 referred to above is, as best shown in FIGS. 1and 2, secured to an outer peripheral portion of the outer member 1through the first and second contact fixing elements 22 a and 22 b ofthe strain generating member 22 so that the first and second contactfixing elements 22 a and 22 b can be held in the same phase relative toeach other with respect to the direction circumferentially of the outermember 1. By positioning the first and second contact fixing elements 22a and 22 b in the same phase relative to each other, the length of thestrain generating member 22 can be reduced and, therefore, the strainsensor unit 21 can easily be installed.

The strain sensor unit 21 is fitted to the outer member 1 in a fashionas described below: As best shown in FIG. 3, the first and secondcontact fixing elements 22 a and 22 b of the strain generating member 22is formed with respective bolt insertion holes 25 and 26 extendingcompletely in an axial direction and in a radial direction,respectively. On the other hand, the flange surface 1 aa and the outerperipheral surface 1 b of the outer member 1 are formed with bolt holes27 and 28 at positions alignable with the bolt insertion holes 25 and26, respectively. When a bolt 29 inserted from the outboard side intothe bolt insertion hole 25 in the first contact fixing element 22 a isthreaded into the bolt hole 27 in the flange surface 1 aa of the outermember 1 and a bolt 30 inserted from an outer peripheral side into thebolt insertion hole 26 of the second contact fixing element 22 b isthreaded into the bolt hole 28 in the outer peripheral surface 1 b ofthe outer member 1, the strain sensor unit 21 is fixed to the outermember 1.

The strain generating member 22 is made of such a material and formed tohave such a shape that will not undergo any plastic deformation when itis fixed to the outer member 1. Also, the strain generating member 22must be of such a shape that it does not undergo a plastic deformationeven when the maximum load expected on the wheel support bearingassembly is imposed thereon. The maximum expected force referred toabove means the maximum force expected during the travel of theautomotive vehicle that does not lead to any automotive accident. Thatis because once the plastic deformation occurs in the strain generatingmember 22, the deformation occurring in the outer member 1 will not betransferred accurately to the strain generating member 22 and wherebytherefore, because the strain measurement will be affected.

For the sensor element 23, various types may be employed. The sensorelement 23 may be employed in the form of a metallic foil strain gauge,a semiconductor strain gauge or a thick film type sensor. By way ofexample, where the sensor element 23 is employed in the form of themetallic foil strain gauge, considering the durability of this metallicfoil strain gauge, it is preferred that the amount of strain occurringin the strain sensor mounting area in the strain generating member 22 is1500 microstrain or lower even when the maximum expected load is imposedon the wheel support bearing assembly. By the same token, where thesensor element 23 is structured by the semiconductor strain gauge, theamount of the strain is preferably microstrain or lower. Also, where thesensor element 23 is structured by the thick film sensor, the amount ofthe strain is preferably 1500 microstrain or lower.

As best shown in FIG. 1, the sensor element 23 of the strain sensor unit21 is connected to an acting force calculating section 31. The actingforce calculating section 31 calculates a force acting between a tire ofthe vehicle wheel and a road surface in response to an output signal ofthe sensor element 23. This acting force calculating section 31 includesa relation setting segment (not shown), in which the relation betweenthe force acting between the wheel tire and the road surface and theoutput signal of the sensor element 23 is set in the form of a computingequation or a table, and is operable in response to the output signalinputted thereinto to output a working force using the relation settingsegment referred to above. The contents set in the relation settingsegment referred to above is set by determining through a series oftests and/or simulations.

Referring now to FIG. 2, a circuit box 32 including the acting forcecalculating section 31 and others is fitted to the outer peripheralsurface 1 b of the outer member 1. A cable 33 is drawn from the sensorelement 23 of the strain sensor unit 21 and wired along the flange 1 aof the outer member 1, to extend into the circuit box 32 and is thenconnected with the acting force calculating section 31 through a ferritecore 34. By inputting the output signal from the sensor element 23 tothe acting force calculating section 31 through the ferrite core 34,influences caused by electromagnetic noises on the output signal of thesensor element 23 can be avoided.

Although the circuit box 32 accommodating therein circuit components forprocessing outputs from the strain sensor unit 21 provided in the wheelsupport bearing assembly is typically provided in an electronic controlunit (ECU) of the automotive vehicle, the provision of the circuit box32 in the vicinity of the strain sensor unit 21 in the wheel supportbearing assembly such as that in the illustrated embodiment is effectiveto simplify labors required in wiring the strain sensor unit 21 to thecircuit box 32 and the circuit box 32 can be installed compactly ascompared with the case in which the circuit box 32 is installed at alocation other then the wheel support bearing assembly.

The operation of the sensor equipped wheel support bearing assembly ofthe structure hereinabove described will now be described. When duringthe travel of the automotive vehicle the load is imposed on the hub unit9, the outer member 1 undergoes a deformation through the rollingelements 5 and such deformation is transferred to the strain generatingmember 22 fitted to the outer member 1, accompanied by deformation ofthe strain generating member 22. The strain induced in the straingenerating member 22 is measured by the sensor element 23. At this time,the radially oriented portion 22 c of the strain generating member 22deforms in accord with deformation of the flange 1 a of the outer member1. In the case of the illustrated embodiment now under discussion, sincethe strain generating member 22 is so structured that the radiallyoriented portion 22 c has a lower rigidity as compared with that of theouter member 1 and that such strain generating member 22 may representan L-shaped configuration including the radially oriented portion 22 cand the axially oriented portion 22 d having a rigidity higher than thatof the radially oriented portion 22 c, strains concentrate on a portionproximate to a corner area lying between the radially oriented portion22 c and the axially oriented portion 22 d and on the side of theradially oriented portion 22 c and, accordingly, the strain larger thanthat in the outer member 1 develops there. In other words, the straindeveloped between the radially oriented portion 22 c and the axiallyoriented portion 22 d represents a transferred and expanded form of thestrain at an R portion in the base end of the flange 1 a. Since thisstrain is measured by the sensor element 23, the strain occurring in theouter member 1 can be detected with a high sensitivity and the strainmeasuring accuracy can be increased.

Since change in strain varies depending on the direction and themagnitude of the load, by determining the relation between the strainand the load beforehand by means of a series of experiments and/orsimulations, the external force acting on the wheel support bearingassembly or the force acting between the wheel tire and the road surfacecan be calculated. The acting force calculating section 31 referred topreviously is operable to refer to the relation between the strain andthe load, preset by means of the experiments and/or simulations ashereinabove described, to calculate the external force acting on thewheel support bearing assembly or the force acting between the wheeltire and the road surface in response to the output of the sensorelement 23. Also, by outputting the output indicative of the externalforce acting on the wheel support bearing assembly or the force actingbetween the wheel tire and the road surface, a meticulous vehiclecontrol can be achieved.

In particular, in this first embodiment of the present inventiondescribed hereinabove, since the sensor mounting surface 22 ca of thestrain generating member 22 in the strain sensor unit 21 is providedwith the covering member 24, made of the over-molded resin or theelastomer bonded by vulcanization, to thereby cover at least the sensorelement 23 in a sealing fashion with this covering member 24, it ispossible to avoid any possible damage and/or malfunction of the sensorelement 23 which would result from external environments (ingress ofmuddy water, collision with foreign matter or the like). As a result, itis possible to detect the strain with a high accuracy for a prolongedperiod of time. Also, since it is possible to avoid the sensor element23 from being affected by influences of external electromagnetic noises,a further highly accurate strain measurement can be accomplished.

FIG. 4 illustrates a modification of the cable 33 drawn outwardly fromthe sensor element 23 in the strain sensor unit 21 employed in thepractice of the first embodiment of the present invention describedhereinabove. In this modification, the cable 33 of the sensor element 23is drawn from a bottom surface of the axially oriented portion 22 d ofthe strain generating member 22, that is, a portion of the surface 22 daopposed to the outer peripheral surface 1 b of the outer member 1 andproximate to the second contact fixing element 22 b in a peripheraldirection along the outer peripheral surface 1 b of the outer member 1.The cable 33 is then connected with the calculating means 31 within thecircuit box 32. In this case, a portion of the cable 33 extending alongthe outer peripheral surface 1 b of the outer member 1 is fixed to theouter peripheral surface 1 b of the outer member 1 by means of a clampmember 35 equipped with a ferrite core 34.

The clamp member 35 equipped with the ferrite core 34 is, as shown inFIG. 5A, of, for example, a thick walled cylindrical shape and has asecuring flange 35 a protruding outwardly therefrom. It is fixed to theouter member 1 by means of a bolt inserted through a hole 41 defined inthe securing flange 35 a. It is to be noted that the clamp member 35 maybe of a type overlapped with two semi-cylindrical pieces having flangemembers 35 a overlapping one above the other.

In the case of this modification, since the cable 33 of the sensorelement 23 may be wired along the outer peripheral surface 1 b of theouter member 1, the cable 33 will not constitute any obstruction ascompared with the wiring thereof along the flange 1 a and the influencesof the electromagnetic noises on the output signal of the sensor element23 can also be reduced.

Also, since the cable 33 is fixed to the outer peripheral surface 1 b ofthe outer member 1 by means of the clamp member 35 equipped with theferrite core 34, the resistance to noises of the signal path extendingfrom the sensor element 23 to the acting force calculating section 31within the circuit box 32 can be increased. Moreover, when the ferritecore 34 having a function of effectively attenuating high frequencycomponents such as electromagnetic noises is added to the clamp member35, no extra space is required for installation of the ferrite core 34and fixing of the ferrite core 34 can be accomplished easily.

It is to be noted that the clamp member 35 may, as shown in FIG. 5B, bein the form of a saddle shaped element made of a sheeting capable ofabsorbing electromagnetic waves or having the electromagnetic waveabsorbing sheeting applied to a surface thereof. In such case, the clampmember 35 is fixed to a surface of the outer member 1 by means of boltsinserted into holes defined at opposite ends of the clamp member 35located in the vicinity of the cable 33 so as to extend completelytherethrough, with the cable 33 held in a fashion urged against thesurface of the outer member 1.

It is to be noted that although the strain sensor unit 21 employed inthe practice of this first embodiment has been shown and described asemploying only one sensor element 23 fitted to the strain generatingmember 22, a plurality of sensor elements 23 may be fitted to the straingenerating member 22. When the plurality of the sensor elements 23 arefitted to the strain generating member 22, a further highly accurateload detection can be accomplished.

Also, in the first embodiment described hereinabove, the strain sensorunit 21 has been shown and described as fitted to only one location ofthe outer member, but the strain sensor unit 21 may be fitted to two ormore locations. When the strain sensor unit 21 is fitted to two or morelocations, a further highly accurate load detection can be accomplished.

In the modification shown in and described with particular reference toFIG. 4, the covering member 24 can be dispensed with, and a firstmodified form in such case is as follows.

[First Modified Form]

The sensor equipped wheel support bearing assembly according to thisfirst modified form of the present invention is a wheel support bearingassembly for supporting a vehicle wheel rotatably relative to a vehiclebody, including: an outer member having an inner periphery formed with aplurality of rolling surfaces; an inner member having rolling surfacesdefined therein in face-to-face relation with the respective rollingsurfaces in the outer member; a plurality of rows of rolling elementsinterposed between those rolling surfaces; and a strain sensor unit,made up of a strain generating member and a sensor element fitted to thestrain generating member for detecting strains induced in the straingenerating member, is fitted to one of the outer and inner members, thatserves as a stationary member; in which the strain generating memberincludes first and second contact fixing elements fixed to respectivelocations of the stationary member, the first contact fixing elementbeing fixed to a flange surface provided in the stationary member andthe second contact fixing element being fixed to a peripheral surface ofthe stationary member, and in which the sensor element in the strainsensor unit is provided with a cable drawn outwardly from a locationproximate to the second contact fixing element in the strain generatingmember fixed to the peripheral surface of the stationary member in adirection circumferentially of the stationary member.

According to this construction, since the cable of the sensor elementcan be wired along the peripheral surface of the stationary member, thecable will not constitute any obstruction as compared with the wiring ofthe cable along the flange of the stationary member and influencesbrought about by the electromagnetic noises on the output signal of thesensor element can also be reduced.

Hereinafter, a second embodiment of the present invention will bedescribed in detail with particular reference to FIGS. 6 to 11. Even inthis second embodiment, like parts similar to those referred to inconnection with the first embodiment are designated by like referencenumerals and, therefore, the details thereof are not reiterated for thesake of brevity.

As shown in FIG. 6, the outer member 1 serves as the stationary memberand has an outer periphery formed with a flange 1 a adapted to besecured to a knuckle of a suspension system of the automotive vehicle,and is of one piece construction including a first boss BS1 formedintegrally with this flange surface 1 aa and a second boss BS2 formedintegrally with a peripheral surface of this outer member 1. The flange1 a is provided with a vehicle body fitting hole 14 at a plurality oflocations in the circumferential direction thereof.

A strain sensor unit 21 shown in FIG. 8 is provided in an outerperipheral portion of the outer member 1. The strain sensor unit 21 ismade up of a strain generating member 22 and a sensor element 23 fittedto this strain generating member 22 for measuring the strain induced inthis strain generating member 22. The strain generating member 22includes a first fixing surface 22 aa and a second fixing surface 22 bbboth defined therein. The first boss BS1 is formed integrally with aportion in the vicinity of the vehicle body fitting hole 14 in the outermember 1, and the first fixing surface 22 aa referred to above is fixedto a foremost end face BS1 a of this first boss BS1 in contacttherewith. The foremost end face BS1 a of the first boss BS1 is formedin a round shape when viewed from an axial direction. The geometricaltolerance of the flatness of this foremost end face BS1 a, whichdecreases a variation in outer dimension of the foremost end face BS1 a,that is, the length L1 of axial projection from a outer member body 1A,is reduced. Accordingly, it is possible to fix a sensor deformingfulcrum.

The second boss BS2 is formed integrally with the outer peripheralsurface of the outer member 1, and the second fixing surface 22 bb isfixed to a foremost end face BS2 a of this second boss BS2 in contacttherewith. The foremost end face BS2 a of the second boss BS2 is formedin a round shape when viewed from a radial direction. The geometricaltolerance of the flatness of this foremost end face BS2 a, whichdecreases a variation in outer dimension of the foremost end face BS2 a,that is, the length L2 of radial projection from a outer member body 1A,is reduced. Accordingly, it is possible to fix a sensor deformingfulcrum. It is to be noted that the shape of each of the first andsecond bosses BS1 and BS2 may not be always limited to the round shapesuch as shown and described, but may be of, for example, a rectangularshape.

A female screw member 72 is formed in part in the first boss BS1 and inpart in the outer member body 1A so as to extend in the axial direction.This female screw member 72 confronts outwardly at a foremost end faceBS1 a of the first boss BS1. With the first fixing surface 22 aa held incontact with the foremost end face BS1, a fixing element in the form ofa bolt 76 is threaded into the female screw member 72 through a boltinsertion hole 70 formed in the first fixing surface 22 aa to therebyfix. Also, a female screw member 73 is formed in part in the second bossBS2 and in part in the outer member body 1A so as to extend in theradial direction. This female screw member 73 confronts outwardly at aforemost end face BS2 a of the second boss BS2, and with the secondfixing surface 22 bb held in contact with the foremost end face BS2 a, afixing element in the form of a bolt 76 is threaded into the femalescrew member 73 through a bolt insertion hole 71 formed in the secondfixing surface 22 bb to thereby fix. The outer member body 1A referredto above is analogous to a body portion of the outer member 1 excludingthe first and second bosses BS1 and BS2.

Also, the strain generating member 22 is of an L-shaped configurationincluding a radially oriented portion 22 ak extending in a radialdirection and having the first fixing surface 22 aa, and an axiallyoriented portion 22 bj including the second fixing surface 22 bb. Of theradially oriented portion 22 ak and the axially oriented portion 22 bj,the wall thickness t1 is, for example, formed to have a value smallerthan the wall thickness t2 as shown in FIG. 8 so that the radiallyoriented portion 22 ak may have a rigidity lower than that of theaxially oriented portion 22 bj. Also, the radial length of the radiallyoriented portion 22 ak and the axial length of the axially orientedportion are so formed as to be the same or so that the radial length maybe longer than the axial length. The sensor element 23 is fitted to theradially oriented portion 22 ak.

The strain generating member 22 referred to above is made of such amaterial and formed to have such a shape that it will not undergo anyplastic deformation when fitted to the outer member 1. Also, the straingenerating member 22 is of such a shape that it does not undergo aplastic deformation even when the maximum load expected on the wheelsupport bearing assembly is imposed thereon. The maximum expected forcereferred to above means the maximum force expected during the travel ofthe automotive vehicle that does not lead to any automotive accident.That is because once the plastic deformation occurs in the straingenerating member 22, the deformation occurring in the outer member 1will not be transferred accurately to the strain generating member 22and whereby the strain measurement will be affected.

The strain generating member 22 may be prepared by means of, forexample, a press work. In such case, it is possible to reduce the costas compared with the case in which the strain generating member isprepared by means of a mechanical processing such as, for example, acutting process. Also, the strain generating member 22 may be a sinteredmetallic product formed by the use of a metal injection molding. Themetal injection molding is one of molding techniques used in moldingmetals and inter-metal compounds, which includes a step of kneading ametal powder with a binder, a step of injection molding with the use ofthe resultant kneaded mixture, a step of degreasing the molded product,and a step of sintering the molded product. According to this metalinjection molding, as compared with the standard powdery metallurgy,such advantages can be obtained that a sintered product having a highsintering density can be obtained, that the sintered metallic productcan be manufactured to a highly accurate dimension and that themechanical strength is also high. Also, the radially oriented portion 22ak and the axially oriented portion 22 bj may have substantially thesame wall thickness and a part of the radially oriented portion 22 akmay be formed with a fragile area (not shown). In this way, the radiallyoriented portion 22 ak can have a rigidity lower than that of theaxially oriented portion 22 bj.

The strain generating member 22 is, in a manner similar to thataccording to the previously described first embodiment, provided with acovering member 24, shown by the double dotted chain line, that coversat least the sensor element 23 in a sealing fashion, which member 22extends from the first fixing surface 22 aa, which is a sensor mountingsurface, to the second fixing surface 22 bb, which is a surface of theaxially oriented portion 22 bj, which is opposed to the outer peripheralsurface 1 b of the outer member (FIG. 6). It is to be noted that thecovering member 24 may be of a type capable of covering the entiresurface of the strain generating member 22. This covering member 24 ismade of a resinous material that is over-molded on that surface regiondiscussed above or an elastomer (NBR, H-NBR, acrylic resin and so on)that is bonded by vulcanization. The over-molded resinous material maybe suitably employed in the form of any one of the following materials:

Resins of the polyamide system: 66 Nylon, PPA (polyphthalamide) or thelike.

Synthetic resin of the special ether system: PPS or the like.

The above-listed materials added with glass fibers.

The covering member 24 shown in FIG. 8 may not be always essential andmay be dispensed with.

The strain sensor unit 21 referred to above is fixed to the outerperipheral portion of the outer member 1 through the first and secondcontact fixing surface 22 aa and 22 bb of the strain generating member22 so that, as best shown in FIG. 7, the first and second contact fixingsurface 22 aa and 22 bb are held in the same phase relative to eachother with respect to the circumferential direction of the outer member1. Also, as best shown in FIG. 11, the strain sensor unit 21 may befixed to a flange 1 c provided between neighboring flanges 1 a in theouter member 1. When the first and second contact fixing surface 22 aaand 22 bb are held in the same phase relative to each other, the lengthof the strain generating member 22 can be reduced and, therefore, thestrain sensor unit 21 can easily be installed. In the case of thisembodiment, the sensor element 23 is fixed within a recessed portion 22ab, formed in the first fixing surface 22 aa of the strain generatingmember 22 by the use of, for example, a bonding agent. The recessedportion 22 ab referred to above is processed in conformity with theshape of the sensor element 23 and, accordingly, it is possible tosecure the adhesion between the strain generating member 22 and thesensor element 23. Also, the positioning accuracy of the sensor element23 relative to the strain generating member 22 can be increased.

As shown in FIG. 6, for processing an output from the sensor element 23,there are provided an acting force calculating section 31 and anabnormality determining section 32. The acting force calculating section31 and the abnormality determining section 32 may be provided in anelectronic circuit device (not shown) such as, for example, a circuitsubstrate fitted to the outer member 1 or the like of the wheel supportbearing assembly or in an electric control unit (ECU) of the automotivevehicle.

The operation of the sensor equipped wheel support bearing assembly ofthe construction hereinabove described will now be described. Whenduring the travel of the automotive vehicle the load is imposed on thehub unit 9 shown in FIG. 6, the outer member 1 undergoes a deformationthrough the rolling elements 5 and such deformation is transferred tothe strain generating member 22 fitted to the outer member 1,accompanied by deformation of the strain generating member 22. Thestrain induced in the strain generating member 22 is measured by thesensor element 23. At this time, the radially oriented portion 22 ak ofthe strain generating member 22 deforms in accord with deformation ofthe flange 1 a of the outer member 1.

In the case of this second embodiment now under discussion, since thestrain generating member 22 is so structured that the radially orientedportion 22 ak has a lower rigidity as compared with that of the outermember 1 and that such strain generating member 22 may represent anL-shaped configuration including the radially oriented portion 22 akhaving a relatively low rigidity and the axially oriented portion 22 bjhaving a high rigidity, strains concentrate on a portion proximate to acorner area 22 cc lying between the radially oriented portion 22 ak andthe axially oriented portion 22 bj and on the side of the radiallyoriented portion 22 ak and, accordingly, the strain larger than that inthe outer member 1 develops there. In other words, the strain developedbetween the radially oriented portion 22 ak and the axially orientedportion 22 bj represents a transferred and expanded form of the strainat an R portion 1 b in the base end of the flange 1 a. Since this strainis measured by the sensor element 23, the strain occurring in the outermember 1 can be detected with a high sensitivity and the strainmeasuring accuracy can be increased.

Although the strain sensor unit 21 employed in the practice of thesecond embodiment has been shown and described as being of thestructure, in which only one sensor element 23 is fitted to the straingenerating member 22, it may be of a structure, in which a plurality ofsensor elements 23 are fitted to the strain generating member 22. Insuch case, the strain can be measured at a plurality of locations of thestrain generating members 22 and, therefore, a further highly accurateload detection can be accomplished. Also, even when a trouble occurs inone of the strain sensor units, the load can be detected by the othersurviving strain sensor units.

Also, although in this second embodiment the strain sensor unit 21 hasbeen shown and described as provided at one location in thecircumferential direction of the outer member 1, it may not be alwayslimited thereto. For example, as shown in FIG. 10, the strain sensorunit 21 may be provided at two or more locations in the circumferentialdirection of the outer member 1. Those plural strain sensor units 21 maybe arranged having been spaced from each other at intervals of asuitable random distance or equidistantly in the circumferentialdirection. Thus, when the strain sensor units 21 are provided at two ormore locations in the circumferential direction of the outer member 1, afurther highly accurate load detection can be accomplished.

Since the sensor equipped wheel support bearing assembly of theconstruction hereinabove described is such that the strain sensor unit21 made up of the strain generating member 22 and the sensor element 23is fitted to the outer member 1 which serves as the stationary member,the load detecting sensor can be installed compactly in the automotivevehicle. Since the strain generating member 22 is a simple componentpart that is fitted to one of the outer member 1 and the inner member 2that serves as the stationary member, it can be excellent in massproductivity and the cost can be reduced by fitting the sensor element23 to this strain generating member 22.

Also, since the strain sensor unit 21 is fitted to the outer member 1through the sensor fixing bosses BS1 and BS2 that are formed in theouter member 1, the following functions and effects can be obtained.Displacement of the sensor fixing bosses BS1 and BS2 relative to theouter member body 1A is prevented. Accordingly, an undesirable movementof the sensor deforming fulcrum can be avoided assuredly and, hence,variation of the sensor strain sensitivity can be reduced.

Since the strain generating member 22 includes the first fixing surface22 aa adapted to be fixed to the foremost end face BS1 a of the firstboss BS1 in contact therewith and the second fixing surface 22 bbadapted to be fixed to the foremost end face BS2 a of the second bossBS2, where the first and second bosses BS1 and BS2 have substantiallythe same projecting length, the first and second fixing surfaces 22 aaand 22 bb differ in position in the radial direction from each other.Accordingly, the strain occurring in the outer member 1 can be made easyto be transferred to and expanded in the strain generating member 22.Since the transferred and expanded strain is measured by the sensorelement 23, the strain occurring in the outer member 1 can be detectedwith a high sensitivity and the accuracy of measurement of the load canbe increased.

Since the first and second fixing surfaces 22 aa and 22 bb of the straingenerating member 22 are fixed to the outer member 1 through the firstand second bosses BS1 and BS2 by means of the respective fixing membersbolts 76, as compared with fixing of the strain generating member bymeans of a bonding agent or welding, the quality of work can beuniformed to reduce the number of work steps and the cost ofmanufacturing can also be reduced. It is to be noted that in addition tofixing of the strain generating member 22 with the use of the bolts, atleast one of the bonding agent and the welding may be employed. In suchcase, the strain generating member 22 can be firmly secured to the outermember 1. Also, as an alternative ways in place of the bolt fixing, pinfixing or welding may be employed.

In the practice of the second embodiment shown in and described withparticular reference to FIGS. 6 to 11, the use of the covering member 24may be dispensed with, in which case a first aspect of application is asfollows:

[First Aspect of First Mode]

The sensor equipped wheel support bearing assembly according to thefirst aspect of the first mode is a wheel support bearing assembly forsupporting a vehicle wheel rotatably relative to a vehicle body;including an outer member having an inner periphery formed with aplurality of rolling surfaces, an inner member having rolling surfacesdefined therein in face-to-face relation with the respective rollingsurfaces in the outer member, a plurality of rows of rolling elementsinterposed between those rolling surfaces, a sealing device for sealingan end portion of a space defined between the outer member and the innermember, a sensor fixing boss formed in one of the outer member and theinner member, that serves as a stationary member, and a strain sensorunit, made up of a strain generating member and at least one or moresensor elements fitted to this strain generating member for detectingstrains induced in the strain generating member, the strain sensor unitbeing fitted to the stationary member through the sensor fixing boss.

[Second Aspect of First Mode]

In the first aspect of the first mode, the sensor fixing boss mayinclude a first boss formed with the flange surface provided in thestationary member and a second boss formed with the peripheral surfaceof the stationary member, and wherein the strain generating memberincludes a first contact fixing element adapted to be fixed to aforemost end face of the first boss in contact therewith and a secondcontact fixing element adapted to be fixed to a foremost end face of thesecond boss in contact therewith

[Third Aspect of First Mode]

In the first aspect of the first mode, the stationary member may be theouter member. In such case, the sensor unit is fitted to the outerperipheral surface of the outer member.

[Fourth Aspect of First Mode]

In the first aspect of the first mode, the sensor fixing boss ispreferably formed integrally with the stationary member. In such case,the number of component parts used can be reduced, the structure can besimplified, and the cost during the mass production can be assuredlyreduced.

[Fifth Aspect of First Mode]

In the first aspect of the first mode, an acting force calculatingsection may be provided for calculating a force acting between the wheeltire and the road surface or an external force acting on the wheelsupport bearing assembly in response to an output of the strain sensorunit.

[Sixth Aspect of First Mode]

In the first aspect of the first mode, fixing of the strain generatingmember to the stationary member may be carried out either by the use ofat least one of a bolt or a pin (both being referred to as a fixingelement) and a bonding agent, by means of the use of both of the fixingelement and the bonding agent, or by the use of a welding technique.Where the strain generating member and the stationary member are fixedtogether by the use of the fixing element, both of the fixing elementand the bonding agent or the welding technique, as compared with thefixing by the use of the welding technique or the like, the quality ofwork can be uniformed to reduce the number of work steps and the cost ofmanufacturing can also be reduced. Where the fixing is carried out bythe use of both of the fixing element and the bonding agent, the straingenerating member can be firmly fixed to the stationary member.

[Seventh Aspect of First Mode]

In the first aspect of the first mode, the strain generating member maybe of an L-shaped configuration including a radially oriented memberextending in the radial direction and an axially oriented memberextending in the axial direction.

In the next place, some examples of application, in which the use of thecovering member shown and described in connection with the firstembodiment is not required, will be described. In the first place, thefirst example of application is shown in FIGS. 12 to 15.

This first applied example is similar to the first embodiment in that itis applied to a third generation model of the wheel support bearingassembly of the inner ring rotating type for the support of a vehicledrive wheel. In this first applied example, like parts similar to thoseemployed in the first embodiment are shown by like reference numeralsand, therefore, the details thereof are not reiterated.

As shown in FIGS. 12 to 15, an outer peripheral portion of the outermember 1 is provided with a strain sensor unit 21. This strain sensorunit 21 is made up of a strain generating member 22 and a sensor element23 provided in the strain generating member 22 for measuring the strainand is fitted to the outer member 1 through first and second contactfixing elements 22 a and 22 b, which are spacer members.

As best shown in FIG. 15, the strain generating member 22 includes afirst fixing surface 22 a adapted to be fixed to a fixing target surfaceFa that is represented by a side face of the flange 1 a of the outermember 1, and a second fixing surface 22 bb adapted to be fixed to afixing target surface Fb that is represented by an outer peripheralsurface of the outer member 1. The strain generating member 22 is of anL-shaped configuration including a radially oriented portion 22 cextending in the radial direction and an axially oriented portion 22 dextending in the axial direction, with an inboard side face foremost endportion of the radially oriented portion 22 b being rendered to be thefirst fixing surface 22 aa and an inner diametric side face foremost endportion of the axially oriented portion 22 d is rendered to be thesecond fixing surface 22 bb. The radially oriented portion 22 c has awall thickness reduced so that the rigidity thereof is lower than thatof the axially oriented portion 22 d. The sensor element 23 is fitted tothe radially oriented portion 22 c that is low in rigidity.

For the sensor element 23, any of various types may be employed. Forexample, the sensor element may be structured with a metallic foilstrain gauge. In such case, it is typically fixed to the straingenerating member 22 by means of bonding.

Also, the sensor element 23 may be employed in the form of a thick filmresistance element on a surface of the strain generating member 22. Thestructure of the sensor element 23 employed in such case is shown inFIG. 16. This sensor element 23 is of a structure in which an insulatinglayer 50 is formed on the surface 22A of the strain generating member22, electrodes 51 and 51 forming a pair are formed on respectiveopposite sides of a surface of this insulating layer 50, a strainmeasuring resistance element 52 in the form of a thick film resistanceelement is formed on the insulating layer 50 at a location intermediatebetween those electrodes 51 and 51, and a protective film 53 is formedover the electrodes 51 and 51 and the strain measuring resistanceelement 52.

A method of making this sensor element 23 will now be shown as follows.At the outset, an insulating material such as, for example, glass isprinted on a surface 22A of the strain generating member 22, which hasbeen prepared from a metallic material such as, for example, stainlesssteel, and is subsequently sintered to form the insulating layer 50.Then, on a surface of the insulating layer 50, an electroconductivematerial is printed and sintered to form the electrodes 51 and 51.Further, between the pair of the electrodes 51 and 51, a material whicheventually forms the resistance element is printed and sintered to formthe strain measuring resistance element 52. Yet, for protecting thoseelectrodes 51 and 51 and the strain measuring resistance element 52, theprotective layer 53 is formed.

The first contact fixing element 22 a is interposed between the firstfixing surface 22 aa of the strain generating member 22 and the sideface of the flange 1 a of the outer member 1 serving as the fixingtarget surface Fa, in which an end face 40 a oriented towards the firstfixing surface 22 aa has a plan shape conforming with that of the firstfixing surface 22 aa and an end face 40 b oriented towards the fixingtarget surface Fa has a plan shape conforming with that of the fixingtarget surface Fa (FIG. 15). On the other hand, the second contactfixing element 22 b is interposed between the second fixing surface 22bb of the strain generating member 22 and the outer peripheral surfaceof the outer member 1 serving as the fixing target surface Fb, in whichan end face 41 a oriented towards the second fixing surface 22 b has theplan shape conforming with that of the second fixing surface 22 bb andan end face 41 b oriented towards the fixing target surface Fb has theplan shape conforming with that of the fixing target surface Fb (FIG.15).

Each of the first and second contact fixing elements 22 a and 22 b isprepared by performing a mechanical processing on a corrosion resistantsteel such as, for example, a stainless steel of the austenite system(for example, SUS304 according to the JIS), a stainless steel of theferrite system (for example, SUS430 according to the JIS) or a rustproofed steel material. In particular, the use of the stainless steel ofthe austenite system having a high rust proofing property is desirable.

The structure of a fitting portion at which the strain sensor unit 21 isfitted to the outer member 1 will now be described (FIG. 13 and FIG.15). The stain generating member 22 is formed with an axially extendingbolt insertion hole 70 extending through the first fixing surface 22 aaand a radially extending bolt insertion hole 71 extending through thesecond fixing element 22 b. Also, the first contact fixing element 22 ais formed with a bolt insertion hole 72 alignable with the boltinsertion hole 70, while the second contact fixing element 22 b isformed with a bolt insertion hole 73 alignable with the bolt insertionhole 71. Further, the outer member 1 is formed with bolt threading holes74 and 75, each having an inner peripheral surface formed with a femalethread, which holes 74 and 75 are positioned at respective locationsalignable with the bolt insertion holes 70 and 72 and also alignablewith the bolt insertion holes 71 and 73. The bolt threading hole 74 ispositioned in the vicinity of the vehicle body fitting hole 14 and thebolt threading hole 75 is positioned on the outer peripheral surface ofthe outer member 1. Also, the bolt threading holes 74 and 75 are held inrespective positions that are in the same phase relative to thecircumferential direction of the outer member 1.

As best shown in FIG. 13, the strain sensor unit 21 is fixed to theouter member 1 by passing a bolt 76 from the outboard side into the boltinsertion hole 70 in the strain generating member 22 and the boltinsertion hole 72 in the first contact fixing element 22 a and thenthreading a male thread portion 76 a of the bolt 76 into the boltthreading hole 74 in the outer member 1, and, on the other hand, bypassing a bolt 76 from an outer peripheral side into the bolt insertionhole 71 in the strain generating member 22 and the bolt insertion hole73 in the second fixing contact portion 22 b and then threading a malethread portion 76 a of the bolt 76 into the bolt threading hole 75 inthe outer member 1.

In a condition in which the strain sensor unit 21 is fixed, as bestshown in FIGS. 12 to 14, the first fixing surface 22 aa of the straingenerating member 22 is fixed to the side face of the flange 1 a in thevicinity of the vehicle body fitting hole 14 in the outer member 1through the first contact fixing element 22 a, while the second fixingsurface 22 bb is fixed to the outer peripheral surface of the outermember 1 through the second contact fixing element 22 b. The first andsecond contact fixing elements 22 a and 22 b have respective end faces40 a and 41 a, oriented respectively towards the fixing surfaces 22 aaand 22 bb of the strain generating member 22, of the same shape as thoseof the fixing surfaces 22 aa and 22 bb and respective end faces 40 b and41 b, oriented respectively towards the fixing target surfaces Fa and Fbof the outer member 1 are of the same shape as those of the fixingtarget surfaces Fa and Fb. Accordingly, the contact fixing elements 22 aand 22 b are held in tight contact with the strain generating member 22and the outer member 1, respectively, to allow the strain generatingmember 22 to be fixed to the outer member 1 in a stabilized posture.Also, since the first and second fixing surfaces 22 aa and 22 bb arefixed so that they assume the respective position that are in the samephase relative to the circumferential direction of the outer member 1,the length of the strain generating member 22 can be reduced and thestrain sensor unit 21 can be installed easily.

As best shown in FIG. 12, for processing an output from the sensorelement 23, there are provided an acting force calculating section 31and an abnormality determining section 32. The acting force calculatingsection 31 is operable to calculate an external force acting on thewheel support bearing assembly or a force acting between a wheel tireand a road surface in response to the output from the sensor element 23in a manner similar to that shown and described in connection with thefirst embodiment. The acting force calculating section 31 includes arelation setting segment (not shown), in which the relation between theforce acting between the wheel tire and the road surface and the outputsignal of the sensor element 23 is set in the form of a computingequation or a table, and is operable in response to the inputted outputsignal to output a working force using the relation setting segmentreferred to above. The contents set in the relation setting segmentreferred to above is set by determining through a series of tests and/orsimulations. The abnormality determining section 32 is operable tooutput an abnormality signal to the outside in the event that theexternal force or the working force calculated by the calculating means31 is determined as exceeding a tolerance value. Those sections may beprovided either in an electronic circuit device (not shown) such as, forexample, a circuit substrate mounted on the wheel support bearingassembly or an electric control circuit (ECU) of the automotive vehicle.

The operation of the sensor equipped wheel support bearing assembly ofthe construction hereinabove described will now be described. Even inthe case of this first applied example, the operation thereof issubstantially identical with that shown and described in connection withthe previously described first embodiment, and particularly in the caseof this first applied example, deformation of the outer member 1 istransferred to the strain generating member 22 through the first andsecond contact fixing elements 22 a and 22 b, resulting in deformationof the strain generating member 22. Since as hereinbefore described,when the first and second contact fixing elements 22 a and 22 b areemployed, the strain generating member 22 can be fixed to the outermember 1 in the stabilized posture, the strain occurring in the outermember 1 is accurately transferred to the strain generating member 22.At this time, the radially oriented portion 22 c of the straingenerating member 22 deforms in accord with deformation of the flange 1a of the outer member 1. In the case of this embodiment, since theradially oriented portion 22 c has a low rigidity as compared with thatof the outer member 1, and the strain generating member 22 is of theL-shaped configuration having the radially oriented portion 22 c of alow rigidity and the axially oriented portion 22 d of a high rigidity,strains tend to concentrate in the vicinity of a corner portion on theside of the radially oriented portion 22 c, which lies between theradially oriented portion 22 c and the axially oriented portion 22 d,and, therefore, show up as a larger strain than that in the outer member1. In other words, the strain developed between the radially orientedportion 22 c and the axially oriented portion 22 d represents atransferred and expanded form of the strain at an R portion 1 b in thebase end of the flange 1 a. Since this strain is measured by the sensorelement 23, the strain occurring in the outer member 1 can be detectedwith a high sensitivity and the strain measuring accuracy can beincreased.

The abnormality determining section 32 is operable to output anabnormality signal to the outside in the event that the external forceacting on the wheel support bearing assembly or the force acting betweenthe wheel tire and the road surface calculated by the calculating means31 is determined as exceeding a tolerance value. This abnormality signalcan be used in a vehicle control of the automotive vehicle. Also, byoutputting the external force acting on the wheel support bearingassembly or the force acting between the wheel tire and the road surfaceon a real time, a meticulous vehicle control can be accomplished.

Since this wheel support bearing assembly is such that the strain sensorunit 21 made up of the strain generating member 22 and the sensorelement 23 is fitted to the outer member 1, the load detecting sensorcan be installed compactly in the automotive vehicle. The processing ofthe wheel support bearing assembly can be minimized and the bearingrigidity will not be lowered. Also, since the strain sensor unit 21 isso structured as to be fitted to the outer member 1 through the firstand second contact fixing elements 22 a and 22 b, not directly to theouter member 1, the strain generating member 22 can have a simplifiedshape such as the L-shaped configuration. Where the strain generatingmember 22 is of the simplified shape, processing of the straingenerating member 22 can be facilitated and the cost can be reduced.Also, where the strain generating member 22 is of the simplified shape,positioning of the sensor element 23 at the fixed position can becarried out precisely. In the case of this first applied example, sincethe surface of the strain generating member 22 where the sensor element23 is provided is a plan surface, fitting of the sensor element 23 tothe strain generating member 22 is easy to achieve. By way of example,the sensor element 23 can be relatively easily formed into a thick filmresistance element.

When the sensor element 23 is structured in the form of a metallic foilstrain gauge or the like, it is generally fixed to the strain generatingmember 22 by means of bonding. However, fixing by means of bondinginvolves the possibility that reduction in bonding strength resultingfrom aging will affect the detection by the sensor element 23. Also,since a bonding works requires a substantial amount of time, it willconstitute a cause of increase of the cost. In contrast thereto, asshown in FIG. 16, by forming the sensor element 23 as a thick filmresistance element on the surface 22A of the strain generating member22, reduction in bonding strength resulting from the aging will notoccur substantially and, accordingly, the reliability of the sensorelement 23 can be increased. Also, since no bonding work for the sensorelement 23 is required, the assemblability can be increased to lower thecost.

Although in the first applied example, the strain sensor unit 21 hasbeen shown and described as provided only at one location, but as shownin FIG. 17, the strain sensor unit 21 may be provided at two or morelocations. When the strain sensor unit 21 is provided at two or morelocations, a further highly accurate load detection can be accomplished.

Although the first applied example is such that the strain generatingmember 22, the first and second contact fixing elements 22 a and 22 band the outer member 1 are fixed in position with the use of the bolts76, they may be fixed in position with the use of a bonding agent. Also,both of the bolts and bonding agent may be employed. In addition,without using any bonding agent and bolts, the strain generating member22, the contact fixing elements 22 a and 22 b and the outer member 1 maybe fixed in position by means of welding. The employment of any of thosefixing structures is effective to firmly fix the strain generatingmember 22, the contact fixing elements 22 a and 22 b and the outermember 1. Also, since the first and second contact fixing elements 22 aand 22 b are made of a stainless steel excellent in corrosionresistance, they will not substantially be corroded even when they areused under the environment in which they are exposed to an external airand/or water. For this reason, displacement of the strain generatingmember 22 relative to the outer member 1 is prevented, and deformationoccurring in the outer member 1 can be accurately transferred to thestrain generating member 22.

FIGS. 18 to 20A and 20B illustrate a second example of application. Thissecond applied example differs from the previously described firstapplied example in that the fixing surfaces 22 e and 22 f provided atthe two locations in the strain generating member 22 of the strainsensor unit 21 are both fixed to the outer peripheral surface of theouter member 1. The axial position of the strain sensor unit 21 is onthe outboard side of the outboard rolling surface 3 and, morespecifically, at a position substantially axially intermediate betweenthe outboard side rolling surface 3 and the outboard end of the outermember 1. Other than the strain sensor unit 21, they are similar tothose shown and described in connection with the first applied example.

As shown in FIG. 19 and FIGS. 20A and 20B, the strain generating member22 of the strain sensor unit 21 is of an elongated arcuate shapeextending in the circumferential direction along the outer periphery ofthe outer member 1, having portions of its inner surface, whichcorrespond to its opposite ends and an intermediate portion thereof,rendered to be fixing surfaces 22 e and 22 f, respectively. The straingenerating member 22 has a sectional shape which is rendered to be, forexample, rectangular, but it may have any suitable sectional shape. Thesensor element 23 is fitted to a front surface at a center portion ofthis strain generating member 22. In the case of this applied example,the sensor element 23 is bonded by the use of a bonding agent.

Between the fixing surfaces 22 e and 22 f of the strain generatingmember 22 and the outer peripheral surface of the outer member 1, whichis a fixing target surface Fb therefor, contact fixing elements 22 a and22 b are intervened. End faces 42 a and 43 a of the contact fixingelements 22 a and 22 b, which are oriented towards the fixing surfaces22 e and 22 f are rendered to be cylindrical surfaces, which conformwith those of the fixing surfaces 22 e and 22 f, while end faces 42 band 43 b oriented towards the outer peripheral surface side of the outermember 1 are rendered to be cylindrical surfaces, which conform with theouter peripheral surface of the outer member 1. The contact fixingelement 22 a at each of opposite ends has a sectional shape, which isrectangular, and also has a large sectional surface area, but thecontact fixing element 22 b at a center portion has a round sectionalshape and also has a small sectional surface area.

This strain sensor unit 21 is fixed to the outer peripheral surface ofthe outer member 1 by means of the fixing surfaces 22 e and 22 f of thestrain generating member 22 through the contact fixing elements 22 a and22 b so that a lengthwise direction of the strain generating member 22may be oriented in a direction circumferentially of the outer member 1.Fixing of the strain generating member 22 and the contact fixingelements 22 a and 22 b and fixing of the contact fixing elements 22 aand 22 b and the outer member 1 are carried out by means of bonding withthe use of, for example, a bonding agent. The fixing may be with the useof bolts. Since the contact fixing elements 22 a and 22 b are such thatthat end faces 42 a and 43 a oriented respectively towards the fixingsurfaces 22 e and 22 f of the strain generating member 22 are of theshape conforming with those of the fixing surfaces 22 e and 22 f and endfaces 42 b and 43 b oriented respectively towards the fixing targetsurface Fb of the outer member 1 are of the shape conforming with thatof the fixing target surface Fb, the contact fixing elements 22 a and 22b are held in tight contact with the strain generating member 22 and theouter member 1, respectively, to allow the strain generating member 22to be fixed to the outer member 1 in a stabilized posture.

The strain sensor unit 21 is to be fixed to the outer member 1 in such amanner that the central fixing surface 22 f may assume a top position inthe entire circumference of the outer member 1 (a position on acounter-road surface side) and the fixing surfaces 22 e at the oppositeends may assume respective positions a few tens degree directly belowthe top position. The top position referred to above is acircumferential location, where the outer member 1 undergoes the mostconsiderable deformation in the radial direction under the influence ofthe load acting on the outer member 1, while the position spaced sometens degrees from the top position is where the outer member 1 does notalmost deform under the influence of the load referred to above. Thishas been ascertained from results of FEM (Finite Elemental Method)analysis. It is to be noted that in the condition, in which the strainsensor unit 21 is fitted to the outer member 1, at portions of thestrain generating member 22 other than the fixing surfaces 22 e and 22 fthereof, a gap is defined between each of them and the outer peripheralsurface of the outer member 1.

Even in this second applied example, in a manner similar to that in thepreviously described first applied example, when the load acts on thehub unit 9, the outer member 1 is deformed through the rolling elements5 and the deformation of the outer member 1 is transferred to the straingenerating member 22 fixed to the outer member 1, accompanied bydeformation of the strain generating member 22. As hereinbeforedescribed, the use of the contact fixing elements 22 a and 22 b iseffective to fix the strain generating member 22 to the outer member 1in a stabilized posture and, therefore, the strain occurring in theouter member 1 can be accurately transferred to the strain generatingmember 22.

The strain generating member 22 undergoes deformation according to thedeformation of the portion of the outer member 1, where the straingenerating member 22 is fixed, in the radial direction. The top positionof the outer member 1, where the central fixing surface 22 f of thestrain generating member 22 is fixed, is the circumferential locationwhere the outer member 1 undergoes the most considerable deformation inthe radial direction as a result of the load while the position at eachof the opposite fixing surface 22 e is fixed is the circumferentiallocation where the outer member 1 does not almost undergo thedeformation as a result of the load. For this reason, the straingenerating member 22 is such that the central portion thereof having thefixing surface 22 f, in which the deformation in the radial direction isconsiderable, is deformed further considerably about a fulcrum that isthen defined at each of the opposite end portions having the fixingsurface 22 e where the deformation in the radial direction is small.Also, since the central contact fixing element 22 b has a rigidity lowerthan that of the contact fixing element 22 a at each of the oppositeends, more considerable deformation occurs at the center portion of thestrain generating member 22 than that at any other portions. When thisconsiderable strain appearing at the center portion of the straingenerating member 22 is measured by means of the sensor element 23, thestrain occurring in the outer member 1 can be detected with a highsensitivity.

The axial position, at which the strain sensor unit 21 is fitted to theouter member 1, is preferably so chosen as to be a position on theoutboard side of the outboard rolling surface 3 in the outer member 1 asis the case with that in the applied example. This is because, in thecase of the position on the outboard side of the outboard rollingsurface 3, the directionality of positive and negative signs will occurin the strain depending on the direction of the load and, therefore, thepositive or negative sign direction of the load can be detected.

According to the FEM analysis and results of experiments, with respectto both of the radially induced strain and the circumferentially inducedstrain of the outer member 1, the strain could have a directionality ina positive sign and a negative sign in response to the positive sign ornegative sign of the load such as, for example, the external force orthe acting force, both referred to previously, occurs merely in aportion on the outboard side in the outer member 1. Accordingly, inorder to detect the positive or negative direction of the load, thestrain sensor unit 21 may be mounted on the outboard position in theouter member 1.

Each of the first applied example and the second applied exampleincludes the following second aspects.

[First Aspect of Second Mode]

The sensor equipped wheel support bearing assembly according to thisfirst aspect of the second mode is a wheel support bearing assembly forsupporting a vehicle wheel rotatably relative to a vehicle body,including an outer member having an inner periphery formed with aplurality of rolling surfaces, an inner member having rolling surfacesdefined therein in face-to-face relation with the respective rollingsurfaces in the outer member, a plurality of rows of rolling elementsinterposed between those rolling surfaces, a strain sensor unit, made upof a strain generating member and at least one sensor element fitted tothis strain generating member for detecting strains induced in thestrain generating member, the strain generating member of the strainsensor unit having two or more fixing surfaces adapted to be fixed totwo locations of the outer member that are spaced a distance from eachother, and a spacer member intervened between each of the fixing surfaceand a fixing target surface of the outer member at which the strainsensor unit is to be fixed, and having an end face oriented towards theside of the fixing face, which end face is of the shape conforming withthat of the fixing face, and also having an end face oriented towardsthe side of the fixing target surface, which end face is of the shapeconforming with that of the fixing target surface.

When during the travel of the automotive vehicle a load acts on one ofthe outer member and the inner member, which serves as a rotatingmember, the rotating member deforms. Also, the deformation of therotating member is transferred to the stationary member through therolling elements, resulting in deformation of the stationary member.Accordingly, regardless of whether the outer member is the rotatingmember or the stationary member, the outer member deforms. Thedeformation of the outer member brings about strain in the straingenerating member through the spacer member. Since the strain generatingmember is fixed relative to the outer member at least two locationsspaced a distance from each other and since two or more deformations ofdifferent degrees are transferred from the outer member, the straingenerating member undergoes a considerable deformation depending on thedifference between those deformations. The strain so induced in thestrain generating member is detected by the sensor element fitted tosuch strain generating member. By determining the relation between thestrain and the load beforehand by means of a series of experimentsand/or simulations, the load imposed on the vehicle wheel can bedetected from the output of the sensor element. The load so detected canbe used in a vehicle control of the automotive vehicle.

Since between each of the fixing surfaces of the strain generatingmember and the fixing target surface of the outer member, the spacermember, in which the end face oriented towards the fixing surface hasthe shape conforming with that of the fixing surface and the end faceoriented towards the side of the fixing target surface has the shapeconforming with that of the fixing target surface, is interposed, thestrain generating member can be fixed to the outer member in astabilized posture. For this reason, the strain occurring in the outermember can be accurately transferred to the strain generating member andthe strain induced in the outer member can be detected with a highprecision accordingly.

The wheel support bearing assembly according to the first aspect of thesecond mode is such that the strain sensor unit made up of the straingenerating member and the sensor element fitted to this straingenerating member is so structured as to be fixed to the outer memberthrough the spacer member, the sensor for the detection of the load canbe installed compactly in the automotive vehicle. The interposition ofthe spacer member between the strain generating member and the outermember makes it possible to simplify the shape of the strain generatingmember. Hence, when the sensor element is fitted to this straingenerating member of the simplified shape, the mass production willbecome excellent and the cost can be reduced. Also, since the processingof the wheel support bearing assembly can be minimized, the bearingrigidity will not be lowered.

[Second Aspect of Second Mode]

In the first aspect, of the two or more spacer member, at least onespacer member may have that end face oriented towards the fixingsurface, which is a plain surface and, also, that end face orientedtowards the side of the fixing target surface, which is a cylindricalsurface.

[Third Aspect of Second Mode]

In the first aspect of the second mode, of the fixing surface of thestrain generating member at the at least two locations, the fixingtarget surface of the first fixing surface may be a side surface of aflange provided in the outer member, and the fixing target surface ofthe second fixing surface may be a peripheral surface of the outermember.

If a contact target surface of the first fixing surface of the straingenerating member is the side surface of the flange provided in theouter member and if a contact target surface of the second fixingsurface is the outer peripheral surface of the outer member, the firstand second fixing surface differ from each other in respect of theirposition in the radial direction and, therefore, the strain occurring inthe outer member comes to be apt to be transferred to and expanded inthe strain generating member. The strain so transferred and expanded ismeasured by the sensor element and, therefore, the strain occurring inthe outer member can be detected with a high sensitivity, accompanied inincrease of the load measuring accuracy.

[Fourth Aspect of Second Mode]

In the first aspect of the second mode, the spacer member referred toabove may be formed of a stainless steel.

Since the spacer member is used under environments in which it tends tobe exposed to an external atmosphere and/or water, the corrosiveresistance is required. For this reason, the stainless steel excellentin corrosive resistance is suited.

[Fifth Aspect of Second Mode]

Also, in the first aspect of the first mode, the fixing target surfaceof the fixing surface of the strain generating member at each of the atleast two locations may be an outer peripheral surface of the outermember.

The degree of deformation in the radial direction of the outer membereffected by the load imposed on the vehicle wheel varies depending onvarious portions in the circumferential direction thereof. According tothe result of analysis, the deformation of the outer member in theradial direction resulting from the axial force acting at the point ofcontact between the wheel tire and the road surface becomes maximum atthe top position, which is on the side of the counter-road surface, andalso at the bottom position, which is on the side adjacent the roadsurface. For this reason, if the fixing surface of a sensor fittingmember is positioned at the at least two locations spaced from eachother in the circumferential direction of the outer member, deformationin the radial direction, which is of a different degree, is brought onthose fixing surfaces. In the strain generating member, the area thereofhaving the fixing surface at which a considerable deformation occurs inthe radial direction undergoes a considerable deformation about thefulcrum that is defined by an area having the fixing surface at which adeformation in the radial direction is small. Accordingly, by fittingthe sensor element to the area having the fixing surface, at which theconsiderable deformation in the radial direction occurs, the strainoccurring in the outer member can be detected by this strain sensor unitwith a high sensitivity.

[Sixth Aspect of Second Mode]

In the first aspect of the second mode, it is recommended to employ anacting force calculating section for calculating an external forceacting on the wheel support bearing assembly or a force acting betweenthe wheel tire and the road surface, in response to an output from thesensor element.

A sectional view of the sensor equipped wheel support bearing assemblyaccording to a suggested example of the present invention is shown inFIG. 21.

As discussed in the “SUMMARY OF THE INVENTION” in connection with thePatent Documents 3 and 4, the inventors of the present invention hasattempted to construct the load sensor unit with a strain generatingmember and a strain measuring sensor element fitted to this straingenerating member and to fix the strain generating member of this loadsensor unit to a peripheral surface of an outer ring. In such case, ithas been ascertained from a series of experiments that in order to allowthe strain occurring in the outer ring to appear considerably, as shownin FIG. 21, the strain generating member 22 of the load sensor unit (thestrain sensor unit) 21 has contact fixing elements 22 a and 22 b fixedto two locations of the outer ring (outer member) 1 and, of them, thefirst contact fixing element 21 a may be fixed to a side face of aknuckle coupling flange 1 a, provided in the outer ring 1 and the secondcontact fixing element 22 b may be fixed to the outer peripheral surfaceof the outer ring 1.

In the meantime, a knuckle 16 forming a part of a suspension system forthe automotive vehicle body is coupled in the following manner to theknuckle coupling flange 1 a. Specifically, in a condition, in which anend face of the knuckle 16 is held in contact with the side face of theflange 1 a, a fastening bolt 18 inserted into a fastening bolt insertionhole 17 in the knuckle 16 is threaded into a vehicle body fitting hole14 defined in the flange 1 a. With this coupling structure, respectivecontact surfaces of the flange 1 a and the knuckle 16 will occasionallyseparate from each other when the load acts on the wheel support bearingassembly in such a direction as to separate the flange 1 a and theknuckle 16 from each other. Once the contact surfaces separate from eachother, the load concentrates on a threaded surface of the vehicle bodyfitting hole 14 and, therefore, the linearity between the load and thestrain detected by the sensor element 23 will be impaired, posing such aproblem that it becomes difficult to accurately detect the load, actingon the wheel support bearing assembly, from the output signal of thesensor element 23.

It is to be noted that where the load acting in such a direction as tourge the flange 1 a towards the knuckle 16 acts on the wheel supportbearing assembly, this load is supported by the entire contact surfacesof the flanges 1 a and the knuckle 16 and, therefore, the linearitybetween the load and the strain detected by the sensor element 23 can bemaintained, making it possible to detect the load, acting on the wheelsupport bearing assembly, from the output signal of the sensor element23.

A third applied example for resolving the above discussed problems willbe described with particular reference to FIGS. 22 to 28. Even in thisthird applied example, like parts similar to those employed in the firstembodiment are shown by like reference numerals and, therefore, thedetails thereof are not reiterated.

As shown in FIG. 22, the outer member 1 serves as the stationary memberand is constructed in a unit of one piece construction. The outer member1 has an outer periphery formed with a flange 1 a adapted to be fittedto a knuckle 16 of a suspension system (not shown) of the automotivevehicle, and a vehicle body fitting hole 14 having an inner peripheryformed with a female thread and extending through the flange 1 a in anaxial direction is provided at a plurality of circumferential locationsof the flange 1 a.

The knuckle 16 is provided with a stepped fastening bolt insertion hole17 defined at a location corresponding to the vehicle body fitting hole14 and, by threading a fastening bolt 18 inserted from the inboard sideinto the fastening bolt insertion hole 17 into the vehicle body fittinghole 14, the knuckle 16 is coupled with the flange 1 a held in contactwith the inboard side face of such flange 1 a. Also, with a nut-likemember 19 provided in contact with an outboard side face of the flange 1a, a portion of the fastening bolt 18 protruding outwardly on theoutboard side from the vehicle body fitting hole 14 is threaded into athreaded hole 19 a defined in the nut-like member 19.

The inner member 2 serves as a rotating member and is made up of a hubunit 9 having a hub flange 9 a for the support of a vehicle wheel and aninner ring 10 mounted on an outer periphery of the inboard end of acylindrical portion 9 b of the hub unit 9. The hub unit 9 and the innerring 10 are formed with respective rolling surfaces 4. An inner ringmounting face 12 of a configuration stepped radially inwardly to have areduced diameter is provided in the outer periphery of the inboard endof the hub unit 9, and the inner ring 10 referred to above is mounted onthis inner ring mounting face 12. The hub unit 9 has a center portionprovided with a throughhole 11. The hub flange 9 a is provided with apress fitting hole 15 defined at a plurality of circumferentiallocations for receiving corresponding hub bolts (not shown). In thevicinity of a root portion of the hub flange 9 a of the hub unit 9, acylindrical pilot portion 13 for guiding a vehicle wheel and a brakecomponent part (not shown) protrudes towards the outboard side.

The outer member 1 has an outer peripheral portion provided with astrain sensor unit 21 shown in FIG. 25A. This strain sensor unit 21 isof a type, in which a sensor element 23 for measuring a straingenerating member 22 is fitted to the strain generating member 22. Thestrain generating member 22 may have various component parts (not shown)for processing an output signal from the sensor element 23 fittedthereto. The strain sensor unit 21 is fitted to the outer member 1through fitting members in the form of first and second contact fixingelements 22 a and 22 b.

The strain generating member 22 includes a first fixing surface 22 aaadapted to be fixed to the nut-like member 19 and a second fixingsurface 22 bb adapted to be fixed to an outer peripheral surface of theouter member 1. The first fixing surface 22 aa is fixed to the nut-likemember 19 through a first contact fixing element 22 a. On the otherhand, the second fixing surface 22 bb is fixed to the outer peripheralsurface of the outer member 1 through a second contact fixing element 22b.

As best shown in FIG. 25B, the strain generating member 22 is of anL-shaped configuration including a radially oriented portion 22 cextending in a radial direction and an axially oriented portion 22 dextending in an axial direction, and a center area of the radiallyoriented portion 22 b is rendered to be the first fixing surface 22 aaand a foremost end area of the axially oriented portion 22 d is renderedto be the second fixing surface 22 bb. The radially oriented portion 22c has a wall thickness reduced so that the rigidity thereof is lowerthan that of the axially oriented portion 22 d. The sensor element 23 isfitted to a portion of a sensor mounting surface 22A, which is aninboard surface of the radially oriented portion 22 c, on a radiallyinward side of the first fixing surface 22 aa.

The strain sensor unit 21 is, as best shown in FIG. 23, fixed to thenut-like member 19 and the outer member 1 with the use of a bolt 76. Thefirst fixing surface 22 aa of the strain generating member 22 is formedwith an axially extending bolt insertion hole 70 and the second fixingsurface 22 bb is formed with a radially extending bolt insertion hole71. The first contact fixing element 22 a is formed with a boltinsertion hole 72 alignable with the bolt insertion hole 70 and thesecond contact fixing element 22 b is formed with a bolt insertion hole73 alignable with the bolt insertion hole 71. The nut-like member 19 isformed with a bolt threading hole 74, having its inner peripheralsurface formed with a female thread, at a position alignable with thebolt insertion holes 70 and 71. Also, the outer member 1 is formed witha bolt threading hole 75, having an inner peripheral surface formed witha female thread, at a position alignable with the bolt insertion holes71 and 73. The bolt threading holes 74 and 75 are held at respectivepositions that are in the same phase with respect to the circumferentialdirection of the outer member 1.

As best shown in FIG. 23, the strain sensor unit 21 is fixed to theouter member 1 by passing a bolt 76 from the outboard side into the boltinsertion hole 70 in the strain generating member 22 and the boltinsertion hole 72 in the first contact fixing element 22 a, with a malethreaded portion 76 a of the bolt 76 engaged into the bolt threadinghole 74 in the nut-like member 19, and, also, by passing a bolt 76 fromthe outer peripheral side into the bolt insertion hole 71 in the straingenerating member 22 and the bolt insertion hole 73 in the secondcontact fixing element 22 b, with a male threaded portion 76 a of thebolt 76 engaged into the bolt threading hole 75 in the outer member 1.

In a condition in which the strain sensor unit 21 is fixed, as shown inFIGS. 22 to 24, the first fixing surface 22 aa of the strain generatingmember 22 is fixed to the nut-like member 19 in contact therewiththrough the first contact fixing element 22 a, and the second fixingsurface 22 bb thereof is fixed to the outer peripheral surface of theouter member 1 in contact therewith through the second contact fixingelement 22 b. Also, the first and second fixing surfaces 22 aa and 22 bbare so fixed as to assume the same phase in the circumferentialdirection of the outer member 1. Thus, if the first and second fixingsurfaces 22 aa and 22 bb are held in the same phase in thecircumferential direction, the length of the strain generating member 22can be reduced, thus facilitating installation of the strain sensor unit21.

As shown in FIG. 22, for processing an output from the sensor element23, there are provided an acting force calculating section 31 and anabnormality determining section 32 as is the case with the previouslydescribed second embodiment. The acting force calculating section 31 andthe abnormality determining section 32 may be those provided in a sensorsignal processing circuit employed in the wheel support bearing assemblyor in an electric control unit (ECU) of the automotive vehicle.

The operation of the sensor equipped wheel support bearing assembly ofthe construction hereinabove described will now be described. When theload is imposed on the hub unit 9 in a manner similar to that in any oneof the foregoing embodiments, the outer member 1 undergoes a deformationthrough the rolling elements 5. Such deformation of the outer member 1is transferred to the strain generating member 22 through the first andsecond contact fixing elements 22 a and 22 b, accompanied by deformationof the strain generating member 22. The strain induced in the straingenerating member 22 is measured by the sensor element 23. At this time,the radially oriented portion 22 c of the strain generating member 22deforms in accord with deformation of the flange 1 a of the outer member1. In the case of this first applied mode, since the rigidity of theradially oriented portion 22 c is lower as compared with that of theouter member 1 and since the strain generating member 22 is of theL-shaped configuration including the radially oriented portion 22 chaving a low rigidity and the axially oriented portion 22 d having ahigh rigidity, the strain concentrates in the vicinity of a corner area22 d between the radially oriented portion 22 c and the axially orientedportion 22 d and on one side adjacent the radially oriented portion 22 cand, hence, appears as a more considerable strain than that in the outermember 1. In other words, the strain developed between the radiallyoriented portion 22 c and the axially oriented portion 22 d represents atransferred and expanded form of the strain at an R portion 1 b (FIG.22) at the base end of the flange 1 a. Since this strain is measured bythe sensor element 23, the strain occurring in the outer member 1 can bedetected with a high sensitivity and the strain measuring accuracy canbe increased.

Since the structure is employed, in which the knuckle 16 and thenut-like member 19 are provided at the opposite side faces of the flange1 a in the outer member 1, respectively, and the both knuckle 16 andnut-like member 19 are fastened together by the bolt 18, the flange 1 aand the knuckle 16 can be maintained in contact with each other. Forthis reason, regardless of whether the load acts on the wheel supportbearing assembly so as to urge the flange 1 a towards the knuckle 16, orwhether the load acts on the wheel support bearing assembly so as toseparate the flange 1 a and the knuckle 16 in a direction away from eachother, a linearity of an output signal of the sensor element 23 relativeto the load can be obtained with the range of the linear characteristicexpanded. For this reason, from the output signal of the sensor element23, the load acting on the wheel support bearing assembly can bedetected without any correction process being effected, or with a simplecorrection process being effected.

Since in this wheel support bearing assembly, the structure is employed,in which the strain sensor unit 21 made up of the strain generatingmember 22 and the sensor element 23 fitted to this strain generatingmember 22 is fitted to the outer member 1, the load detecting sensor canbe installed compactly in the automotive vehicle. Since the straingenerating member 22 is a simple component part that is fitted to theouter member 1 and the nut-like member 19, fitting of the sensor element23 thereto renders the mass productivity to be excellent and also makesit possible to reduce the cost.

Although the foregoing third applied example employs the structure, inwhich the flange 1 a is held down by the nut-like member 19, the flange1 a and the nut-like member 19 may be fixed directly. As a method ofachieving this direct fixing, such fixing methods as shown in FIGS. 26to 28, respectively, are available. In FIG. 26, the nut-like member 19is provided with a shank portion 19 b and, by pressing this shankportion 19 b under interference into the vehicle body fitting hole 14having a smooth inner periphery, the nut-like member 19 is fixed to theflange 1 a. In FIG. 27, the nut-like member 19 is provided with a shankportion and this shank portion is rendered to be a male threaded portion19 c having an outer periphery formed with a threaded groove and, bythreading this male threaded portion 19 c into a female threaded portion14 a defined in the vehicle body fitting hole 14, the nut-like member 19is fixed to the flange 1 a. Although the illustrated examples make useof the threaded hole 19 a in the nut-like member 19 which is in the formof an internally threaded blind hole, it may extend completely in theaxial direction. FIG. 28 illustrates the example, in which in theapplied modes shown in and described with reference to FIGS. 22 to 25Aand 25B, the nut-like member 19 is fixed to the flange 1 a by means of aweld deposit W.

As hereinabove described, if the nut-like member 19 is fixed to theflange 1 a of the outer member 1, a work to connect the flange 1 a andthe knuckle 16 by means of the fastening bolt 18 can be eased. Also,since the position of the nut-like member 19 relative to the flange 1 ais stabilized, the detecting accuracy of the strain sensor unit 21 canbe increased. In addition, by providing the nut-like member 19 in afixed condition relative to the outer member 1, the nut-like member 19will form a substantial part of the flange 1 a and since the couplinglength between the flange 1 a and the fastening bolt 18 increases, thecoupling can be made firm. In addition, by providing the nut-like member19 in a fixed condition relative to the outer member 1, the nut-likemember 19 will form a substantial part of the flange 1 a and since thecoupling length between the flange 1 a and the fastening bolt 18increases, the coupling can be made firm.

Although the third applied example is such that the strain generatingmember 22, the first and second contact fixing elements 22 a and 22 band the outer member 1 are fixed in position with the use of the bolts76, they may be fixed in position with the use of a bonding agent. Also,the both may be employed. In addition, without using any bonding agentand bolts, the strain generating member 22, the contact fixing elements22 a and 22 b and the outer member may be fixed in position by means ofwelding. The employment of any of those fixing structures is effectiveto firmly fix the strain generating member 22, the contact fixingelements 22 a and 22 b and the outer member 1. For this reason,displacement of the strain generating member 22 relative to the outermember 1 is prevented, and deformation occurring in the outer member 1can be accurately transferred to the strain generating member 22.

It is to be noted that although in describing the third applied example,reference has been made that the outer member 1 is the stationarymember, it can be equally applied to the wheel support bearing assembly,in which the inner member serves as the stationary member, in which casethe strain sensor unit 21 is provided on a peripheral surface whichforms an inner periphery of the inner member.

This third applied example includes the following third modes ofapplication.

[First Aspect of Third Mode]

The wheel support bearing assembly according to the first aspect of thethird mode is a wheel support bearing assembly for supporting a vehiclewheel rotatably relative to a vehicle body, including an outer memberhaving an inner periphery formed with a plurality of rolling surfaces,an inner member having rolling surfaces defined therein in face-to-facerelation with the respective rolling surfaces in the outer member, aplurality of rows of rolling elements interposed between those rollingsurfaces, a flange formed in a peripheral surface of one of the outermember and the inner member, that serves as a stationary member, afastening bolt that connects the flange and a knuckle forming a part ofa suspension system of the automotive vehicle, inserted through avehicle body fitting hole defined in the flange, a nut-like memberfitted to the flange for urging a portion of the flange around thevehicle body fitting hole against the knuckle, and a strain sensor unit,made up of a strain generating member fixed to the stationary member anda strain measuring sensor element fitted to the strain generating memberis provided, the strain generating member of the strain sensor unitincluding two contact fixing elements at respective locations relativeto the stationary member, in the form of a first contact fixing elementadapted to be fixed to the nut-like member and a second contact fixingelement adapted to be fixed to a peripheral surface of the stationarymember.

When the load acts on the rotating member during the travel of theautomotive vehicle, the stationary member undergoes deformation throughthe rolling elements and such deformation brings about a strain in thestrain generating member. The sensor element fitted to the straingenerating member outputs an output in response to the strain induced inthe strain generating member. From this output, the strain occurring inthe stationary member can be detected. By determining the relationbetween the strain and the load beforehand by means of a series ofexperiments and/or simulations, the load acting on the vehicle wheel canbe detected from the output of the sensor element. Also, the load sodetected can be used in a vehicle control of the automotive vehicle.

Since the nut-like member for urging that portion of the flange aroundthe vehicle body fitting hole against the knuckle is fitted to theflange, the flange and the knuckle can be held at all times in acontacted fashion. For this reason, regardless of whether a force actson the wheel support bearing assembly in such a direction as to urge theflange against the knuckle, or whether a force acts on the wheel supportbearing assembly in such a direction as to separate the flange and theknuckle away from each other, the linearity of an output signal of thesensor element relative to the load can be maintained and, from theoutput signal of the sensor element, the load imposed on the wheelsupport bearing assembly can be detected with no correcting processbeing effected or with merely a simple correcting process beingeffected.

Since the strain generating member includes two contact fixing elementsat respective locations relative to the stationary and since of thosecontact fixing elements the first contact fixing element is fixed to thenut-like member adapted to contact a flange surface provided in thestationary member while the second contact fixing element is fixed to aperipheral surface of the stationary member, respective radial positionsof the first and second contact fixing elements differ from each otherand the strain occurring in the stationary member comes to appear easilyas transferred and expanded in the strain generating member. Since thesensor element outputs in response to the strain so transferred andexpanded, the strain occurring in the stationary member can be detectedwith a high sensitivity and the load measuring accuracy will increase.

Since this wheel support bearing assembly is of such a construction inwhich the strain sensor unit made up of the strain generating member andthe sensor element fitted to this strain generating member is fitted tothe stationary member, the sensor for the detection of the load can beinstalled compactly in the automotive vehicle. Since the straingenerating member is a simple component part that is fitted to thestationary member, fitting of the sensor element thereto makes the massproductivity to be excellent and makes it possible to reduce the cost.

[Second Aspect of Third Mode]

In the first aspect of the third mode, the stationary member may berepresented by the outer member. In such case, the strain sensor unit isfitted to an outer peripheral surface of the outer member.

[Third Aspect of Third Mode]

In the first aspect of the third mode, the strain generating member maybe of an L-shaped configuration including a radially oriented portionextending in a radial direction and an axially oriented portionextending in an axial direction, in which the sensor element is fittedat a location in the radially oriented portion in the vicinity of apoint of intersection between the radially oriented portion and theaxially oriented portion.

[Fourth Aspect of Third Mode]

In the first aspect of the third mode, the nut-like member may be fixedto the stationary member by press fitting it into the vehicle bodyfitting hole.

[Fifth Aspect of Third Mode]

In the first aspect of the third mode, the nut-like member may be fixedto the stationary member by threading a male threaded portion of thenut-like member into a female threaded portion of the vehicle bodyfitting hole.

[Sixth Aspect of Third Mode]

In the first aspect of the third mode, the nut-like member may be fixedto the stationary member by meals of welding.

By fixing the nut-member beforehand to the stationary member by means ofthe method according to any one of the fourth to sixth aspects of thethird mode, the work to connect the flange of the stationary member andthe knuckle together by means of the fastening bolt can be facilitated.Also, since the position of the nut-like member relative to the flangeis stabilized, the detecting accuracy of the strain sensor unitincreases. In addition, if the nut-like member is provided in a fixedfashion to the stationary member, the nut-like member will become asubstantial part of the flange and the length of a coupling portionbetween the flange and the fastening member will increase and,therefore, the coupling will become firm. In order to increase thelength of the coupling portion between the flange and the fasteningbolt, a projection of the same shape as that of the nut-like member maybe provided in the flange, but in the case of a bearing raceway ringformed by forging, processing of the projection is difficult,accompanied by reduction in yield.

A fourth example of application will now be described with particularreference to FIGS. 29 to 32A and 32B. Even in this fourth appliedexample, like parts similar to those employed in the first embodimentare shown by like reference numerals and, therefore, the details thereofare not reiterated.

As best shown in FIG. 29, the outer member 1 serves as a stationarymember and has an outer periphery formed with a vehicle body fittingflange 1 a adapted to be fitted to a knuckle of a suspension system (notshown) of an automotive vehicle body, with a bolt hole 14 defined inthis flange 1 a at a plurality of locations in a directioncircumferentially thereof. The bolt holes 14 are processed either tohave female threads or not to have them. The flange 1 a referred toabove has a circumferential portion 1 aa, in which the bolt holes 14 areprovided, which portion 1 aa is rendered to be a bolt hole-providedprojecting piece 1A protruding radially outwardly beyond the remainingportion thereof. In this illustrated embodiment, four bolt hole-providedprojecting pieces 1A are provided and are spaced at intervals of apredetermined distance in the circumferential direction. It is, however,to be noted that the bolt hole-provided projecting piece 1A is notalways limited to four such as shown and described. Between theneighboring bolt hole-provided projecting pieces 1A and 1A in an outerperipheral surface of the outer member 1, a sensor fixing projectingpiece SP protruding radially outwardly, specifically in this fourthapplied example now under discussion, one sensor fixing projecting pieceSP is provided.

The outer peripheral surface of the outer member 1 is provided with astrain sensor unit 21. This strain sensor unit 21 is of a type, in whichthe sensor element 23 for detecting the strain induced in a straingenerating member 22 and a sensor signal processing circuit 60 forprocessing an output signal of the sensor element 23 are provided in thestrain generating member 22. The strain sensor unit 21 is fitted to theouter member 1 through first and second contact fixing elements 22 a and22 b, which are fitting members.

The strain generating member 22 includes a first fixing surface 22 aaadapted to be fixed directly to the first contact fixing element 22 a incontact therewith and a second fixing surface 22 bb adapted to be fixeddirectly to the second contact fixing element 22 b in contact therewith.The strain generating member 22 is of an L-shaped configurationincluding a radially oriented portion 22 c extending in a radialdirection and an axially oriented portion 22 d extending in an axialdirection. An area of the radially oriented portion 22 c proximate to anintermediate point thereof in a lengthwise direction is rendered to bethe first fixing surface 22 aa and an area of the axially orientedportion 22 d proximate to a foremost end thereof is rendered to be thesecond contact fixing portion 22 b. The radially oriented portion 22 chas a wall thickness so reduced as to have a reduced rigidity ascompared with that of the axially oriented portion 22 d. The sensorelement 23 is arranged at a location radially inwardly of the firstfixing surface 22 aa in a sensor mounting surface 22A, which is asurface on the inboard side of the radially oriented portion 22 c.

The sensor element 23 referred to above is in the form of a thick filmresistance element formed on the sensor mounting surface 22A of thestrain generating member 22. In other words, an insulating layer isformed on the sensor mounting surface 22A; a pair of electrodes 51 and51 are formed on respective sides of a surface of this insulating layer;a strain measuring resistance element comprised of a thick filmresistance element, which eventually becomes a strain sensor, is formedon the insulating layer at a location between the electrodes 51 and 51;and a protecting film is formed on the strain measuring resistanceelement and the electrodes 51 and 51.

The sensor signal processing circuit 60 includes electric/electroniccomponent parts 23 such as, for example, an operational amplifier forprocessing an output signal of the sensor element 23, resistors, amicrocomputer and circuit elements such as, for example, an electricpower source for driving the sensor element 23, all integrated on asemiconductor chip or the like, and a surface of the insulating layer isformed with an electrode 64 for electrically connecting the sensorelement 23 and the electric/electronic component parts 63 with eachother, an electrode 65, which forms a wiring between the variouscomponent of the electric/electronic component parts 63, and a pad 68for connecting a cable 69, which forms a signal transmitting path fromthe sensor signal processing circuit 60 to an external device such as,for example, an electric control unit (ECU) of the automotive vehicle.

A fitting structure of the strain sensor 21 will now be described indetail.

The outer peripheral surface of the outer member 1 is provided with asensor fixing projecting piece SP protruding in a radially outwarddirection. This sensor fixing projecting piece SP is interposed betweena bolt hole-provided projecting piece 1A in the outer peripheral surfaceof the outer member 1 and a bolt hole-provided projecting piece 1Aneighboring the bolt hole-provided projecting piece 1A and is, as bestshown in FIG. 31, formed in a generally rectangular shape when viewedfrom front. The term “when viewed from front” is analogous to a viewingof an object in an axial direction. A foremost end portion of thissensor fixing projecting piece SP, that is, a radial position P1 of aradially oriented outer edge portion SPa is provided at a position,which forms a portion of, for example, the same pit circle as a radialposition P2 of a radially oriented outer peripheral edge portion of thebolt hole-provided projecting piece 1A. It is, however, to be noted thatit is not always limited to the same pitch circle.

An inboard side surface SP1 of the sensor fixing projecting piece SP,that is, a right side end face shown in FIG. 29 and an inboard sidesurface 1A1 of the bolt hole-provided projecting piece 1A are soprovided as to assume the same position in the axial direction. Thereby,the respective inboard side surfaces SP1 and 1A1 of the sensor fixingprojecting piece SP and the bolt hole-provided projecting piece 1A maybe arranged in a fashion urged against the knuckle. Also, an outboardside surface SP2 of the sensor fixing projecting piece SP that is, aleft end face shown in FIG. 29 and an outboard side surface 1A2 of thebolt hole-provided projecting piece 1A are so provided as to assume thesame position in the axial direction. It is, however, to be noted thatit is not always limited to the same position. Also, the outboard sidesurface SP2 of the sensor fixing projecting piece SP is flattened and isso constructed as to have a capability of being fixed tightly to asurface 40 a of the first contact fixing element 22 a.

In the strain generating member 22, an axially extending bolt insertionhole 70 is formed in the first fixing surface 22 aa of the radiallyoriented portion 22 c and a radially extending bolt insertion hole 71 isformed in the second fixing surface 22 bb of the axially orientedportion 22 d.

In the outer peripheral surface of the outer member 1, at a positionwhich lies in the same phase relative to a circumferential position ofthe sensor fixing projecting piece SP, a pedestal 50 projecting in aradially outward direction is provided. The radially projecting positionof the pedestal 50 referred to above is so provided as to lie radiallyinwardly of the radially projecting position of the sensor fixingprojecting piece SP. The amount of projection Z1 of the pedestal 50 froman outer peripheral surface base end portion of the outer member 1 is,for example, about ½ of the amount of projection Z2 of the sensor fixingprojecting piece SP from the outer peripheral surface base end portion.

An upper surface of the pedestal 50 is flattened to form a flat area 50a and the axially oriented portion 22 d of the strain generating member22 is fixed to this flat area 50 a. The flat area 50 a of this pedestal50 is so formed as to lie vertical relative to a radially extending axispassing through a center of the bearing assembly. One side surface 50 bof the pedestal 50 forms, that is, laps, when viewed from front as shownin FIG. 31, along one side surface SPb of the sensor fixing projectingpiece SP, while the opposite side surface 50 c of the pedestal 50 laps,when viewed from front, along the opposite side surface SPc of thesensor fixing projecting piece SP. The distance between the side surface50 b and the opposite side surface 50 c may be either narrow or parallelin a direction radially outwardly.

The first contact fixing element 22 a is formed with an axiallyextending bolt insertion hole 72 and the sensor fixing projecting pieceSP is formed with an axially extending bolt threading hole 74 having aninner peripheral surface thereof formed with a female thread defined ata location corresponding to the bolt insertion hole 70 in the firstfixing surface 22 aa and the bolt insertion hole 72 in the first contactfixing element 22 a.

The second contact fixing element 22 b is formed with a radiallyextending bolt insertion hole 73 and the pedestal 50 is formed with aradially extending bolt threading hole 75 defined at a locationcorresponding to the bolt insertion hole 71 in the second fixing surface22 bb and the bolt insertion hole 73 in the second contact fixingelement 22 b.

The bolt insertion hole 70 in the radially oriented portion 22 c of thestrain generating member 22 and the bolt insertion hole 72 in the firstcontact fixing element 22 a are so arranged as to be coaxial relative tothe bolt threading hole 74 in the sensor fixing projecting piece SP.Also, the bolt insertion hole 71 in the axially oriented portion 22 d ofthe strain generating member 22 and the bolt insertion hole 73 in thesecond contact fixing element 22 b are so arranged as to be coaxialrelative to the bolt threading hole 75 in the pedestal 50. In thiscondition of arrangement, a bolt 76 is passed from the outboard sideinto the bolt insertion holes 70 and 72. Also, a bolt 76 is insertedfrom the outboard side into the bolt insertion holes 71 and 73. Bythreading the male threads of those bolts 76 and 76 into the boltthreading holes 74 and 75, respectively, the strain sensor unit 21 isfixed to the outer member 1.

In a condition in which the strain sensor unit 21 is fixed, the firstfixing surface 22 aa of the strain generating member 22 is fixed to aradially outward portion of the outboard side surface SP2 in the sensorfixing projecting piece SP in contact therewith through the firstcontact fixing element 22 a. Also, the second fixing surface 22 bb isfixed to the flat area 50 a of the pedestal 50 through the secondcontact fixing element 22 b in contact therewith. Further, the first andsecond fixing surfaces 22 aa and 22 bb are so fixed as to assumerespective positions that lie in the same phase relative to thecircumferential direction of the outer member 1. When the first andsecond fixing surfaces 22 aa and 22 bb are rendered to be in the samephase in the circumferential direction, the length of the straingenerating member 22 can be reduced and, therefore, installation of thestrain sensor unit 21 relative to the outer member 1 is facilitated.

As best shown in FIG. 29, for processing an output from the sensorelement 23, there are provided an acting force calculating section 31and an abnormality determining section 32. The acting force calculatingsection 31 and the abnormality determining section 32 may be providedeither in a sensor signal processing circuit 60 mounted on the wheelsupport bearing assembly or in an electric control unit (ECU) of theautomotive vehicle.

The operation of the sensor equipped wheel support bearing assembly ofthe above described construction will be hereinafter described. When theload is imposed on the hub unit 9, the outer member 1 undergoes adeformation through the rolling elements 5. Such deformation of theouter member 1 is transferred to the strain generating member 22 throughthe first and second contact fixing elements 22 a and 22 b, accompaniedby deformation of the strain generating member 22. The strain induced inthe strain generating member 22 is measured by the sensor element 23. Atthis time, the radially oriented portion 22 c of the strain generatingmember 22 deforms in accord with deformation of the sensor fixingprojecting piece SP of the outer member 1. In the case of this appliedmode, since the strain generating member 22 is of the L-shapedconfiguration, the strain concentrates in the vicinity of a corner areabetween the radially oriented portion 22 c and the axially orientedportion 22 d and on one side adjacent the radially oriented portion 22 cand, hence, the strain appears as a more considerable strain than thatin the outer member 1. In other words, the strain developed at a bentarea 22 ca in the radially oriented portion 22 c represents atransferred and expanded form of the strain at an R portion SPR at abase end of the sensor fixing projecting piece SP. Since this strain ismeasured by the sensor element 23, the strain occurring in the outermember 1 can be detected with a high sensitivity and the strainmeasuring accuracy can be increased.

Also, the inboard side surface SP1 of the sensor fixing projecting pieceSP and the inboard side surface 1A1 of the bolt hole-provided projectingpiece 1A are so provided as to assume the same position in the axialdirection and those inboard side surfaces SP1 and 1A1 of the sensorfixing projecting piece SP and the bolt hole-provided projecting piece1A, respectively, are disposed as urged against the knuckle. Inaddition, since the sensor fixing projecting piece SP is not formedwith, for example, a bolt hole for securement to the vehicle body, it ispossible for the first contact fixing element 22 a to be fixed to anouter diametric portion of this sensor fixing projecting piece SP incontact therewith.

For this reason, as is the case in which the first fixing surface 22 ais provided in the flange 1 a surface for securement to the vehiclebody, it is possible to increase the difference in radial positionbetween the first and second fixing surfaces 22 aa and 22 bb as large aspossible. Accordingly, the strain occurring in the outer member 1 canappear in the strain generating member 22 as transferred and expanded.

Since change of the strain differs depending on the direction and themagnitude of the load, by determining the relation between the strainand the load beforehand by means of a series of experiments and/orsimulations, an external force acting on the wheel support bearingassembly or a force acting between a wheel tire and a road surface canbe calculated. The acting force calculating section 31 referred topreviously makes use of the relation between the strain and the load,preset by means of the experiments and/or simulations, to calculate theexternal force acting on the wheel support bearing assembly or the forceacting between the wheel tire and the road surface from an output of thestrain sensor unit 23. The abnormality determining section 32 referredto previously outputs an abnormality signal to the outside in the eventthat the external force acting on the wheel support bearing assembly orthe force acting between the wheel tire and the road surface, which hasbeen calculated by the acting force calculating section 31, exceeds atolerance value. This abnormality signal can be used in a vehiclecontrol of the automotive vehicle. Also, if the external force acting onthe wheel support bearing assembly or the force acting between the wheeltire and the road surface is outputted on a real time, a meticulousvehicle control can be achieved.

In this sensor equipped wheel support bearing assembly, the first fixingsurface 22 aa of the strain sensor unit 21 is fixed to the radiallyoutwardly protruding sensor fixing projecting piece SP provided betweenthe neighboring bolt hole-provided projecting pieces 1A and 1A in theouter peripheral surface of the outer member 1, through the firstcontact fixing element 22 a. Along therewith, since the second fixingsurface 22 bb of the strain sensor unit 21 is fixed to the pedestal 50on the outer peripheral surface of the outer member 1 through the secondcontact fixing element 22 b, the load detecting sensor can be installedcompactly in the automotive vehicle.

In order to fix a portion of the strain sensor unit 21 to the sensorfixing projecting piece SP, which is a dedicated component part, acontact fixing portion of the sensor fixing projecting piece SP relativeto the strain sensor unit 21 can be provided in tight contact incorrespondence with the strain sensor unit 21 without any additionalprocessing being effected. In this way, the strain generating member 22can be fixed stably on the outer peripheral surface of the outer member1 which is the stationary member. Accordingly, it is possible tosuppress variation in sensor output from the sensor element 23 and tostabilize it. Also, since the strain generating member 22 is a simplecomponent part that can be prepared by the use of, for example, anyknown press work, the strain sensor unit 23 can be provided in thestrain generating member 22 and, as compared with the conventional art,in which a strain gauge is bonded to the outer member, it is possible toincrease the mass productivity and to reduce the cost. However, thestrain generating member 22 is not limited to a product prepared by theuse of press work. In addition, as compared with a portion of a strainsensor being fixed to the bolt hole-provided projecting piece,interference of the strain sensor unit 21 with bolts or the like thatare threadingly engaged in the bolt hole-provided projecting piece 1A isprevented, and the freedom of design can be increased correspondingly.

Also, in the outer peripheral surface of the outer member 1, thepedestal 50 projecting radially outwardly is provided at such a positionthat lies in the same phase as the peripheral position of the sensorfixing projecting piece SP; the upper surface of this pedestal 50 isflattened to provide the flat area 50 a; and the second contact fixingelement 22 b of the strain sensor unit 21 is fixed to this flat area 50a. For this reason, the second contact fixing element 22 b of the strainsensor unit 21 can be provided in tight contact in correspondence withthe flattened surface of the flat area 50 a. Accordingly, anotherportion of the strain sensor unit 21 can be stably and firmly fixed tothe flat area 50 a. The work of fixing such another portion of thestrain sensor unit 21 is effective to reduce the length of time requiredto complete such fixing work and also to lessen the work load.

Although in this fourth applied example, the outer member 1 has beenshown and described as provided with the single sensor fixing projectingpiece SP and that portion of the strain sensor unit 21 has been shownand described as fixed to this sensor fixing projecting piece SP, it isnot always limited to such mode. By way of example, as shown in FIG. 33,a plurality of sensor fixing projecting pieces SP may be provided in theouter member 1, in which case that portion of the strain sensor unit 21is fixed to each of those sensor fixing projecting pieces SP. When thestrain sensor unit 21 is provided at two or more locations, a furtherhighly accurate load detection can be accomplished.

Although the previously described applied example is such that thestrain generating member 22, the first and second contact fixingelements 22 a and 22 b and the outer member 1 are fixed by the use ofthe bolts 76, the fixing may be accomplished by the use of a bondingagent. Also, both of the bolts and the bonding agent may be concurrentlyemployed. In addition, without using any bonding agent and bolts, thestrain generating member 22, the first and second contact fixingelements 22 a and 22 b and the outer member 1 may be fixed in positionby means of welding, or even pins. The employment of any of those fixingstructures is effective to firmly fix the strain generating member 22,the first and second contact fixing elements 22 a and 22 b and the outermember 1. For this reason, displacement of the strain generating member22 relative to the outer member 1 is prevented, and deformationoccurring in the outer member 1 can be accurately transferred to thestrain generating member 22.

The radially oriented portion 22 c of the strain generating member 22and the first contact fixing element 22 a may be provided integrally andthe axially oriented portion 22 d and the second contact fixing portion22 b may be provided integrally. Also, the first and second contactfixing elements 22 a and 22 b may be dispensed with from the componentelements of the strain sensor unit and the radially oriented and axiallyoriented portions of the strain generating member can be fixed directlyto the sensor fixing projecting piece and the pedestal. In such case,the number of component parts used in the sensor equipped wheel supportbearing assembly can be reduced to simplify the assemblage.

As a modified form of the strain sensor unit, a temperature sensor orthe like may be provided in the radially oriented portion 22 c of thestrain generating member 22 as a component separate from the sensorelement 23. For this temperature sensor, a platinum temperaturemeasuring resistor or a thermocouple or a thermistor, for example, maybe employed. In addition, a sensor capable of detecting a temperatureother than that may be employed.

Even in the wheel support bearing assembly equipped with the strainsensor unit of the structure hereinbefore described, the sensor element23 detects the strain induced in the strain generating member 22 so thatthe load acting on the vehicle can be measured from such strain. In themeantime, in the wheel support bearing assembly temperature tends tochange during the use thereof and a change in temperature affects thestrain induced in the strain generating member 22 or the operation ofthe sensor element 23. Accordingly, detecting the temperature of thestrain generating member 22 with the temperature sensor, which isarranged in the strain generating member 22, and correcting an output ofthe sensor element 23 in response to the temperature so detected iseffective to eliminate such influence as brought about by temperature.In this way, a highly accurate load detection can be accomplished.

In the next place, the fourth applied example includes the followingfourth mode.

[First Aspect of Fourth Mode]

The sensor equipped wheel support bearing assembly according to thefirst aspect of the fourth mode is a wheel support bearing assemblyincluding an outer member having an inner periphery formed with aplurality of rolling surfaces, an inner member having rolling surfacesdefined therein in face-to-face relation with the respective rollingsurfaces in the outer member, a plurality of rows of rolling elementsinterposed between those rolling surfaces, a vehicle body fitting flangeformed in a peripheral surface of one of the outer member and the innermember, that serves as a stationary member, and adapted to be fitted toa knuckle, the flange being provided with a bolt hole that is defined ata plurality of locations in a direction circumferentially thereof,circumferential portions of the flange, where the corresponding boltholes are defined, protruding in an outer diametric direction beyond anyother portion thereof to render such flange to be a bolt hole-providedprojecting piece, and a sensor fixing projecting piece protrudingradially outwardly provided in an outer peripheral surface of thestationary member and between the neighboring bolt hole-providedprojecting pieces, in which a portion of a sensor unit including astrain generating member and a sensor element fitted to the straingenerating member is fixed to the sensor fixing projecting piece whileanother portion of the strain sensor unit is fixed to the outerperipheral surface of the stationary member.

When the load acts on the rotating member during the travel of theautomotive vehicle, the stationary member undergoes deformation throughthe rolling elements and such deformation brings about a strain in thestrain sensor. The strain sensor unit detects the strain induced in thestrain generating member. By determining the relation between the strainand the load beforehand by means of a series of experiments and/orsimulations, the load acting on the vehicle wheel can be detected froman output of the strain sensor unit. Also, the load so detected can beused in a vehicle control of the automotive vehicle.

The sensor equipped wheel support bearing assembly according to thefirst aspect of the fourth mode is such that the strain generatingmember and a portion of the strain sensor unit fitted to this straingenerating member is fixed to the sensor fixing projecting pieceprotruding radially outwardly in the outer peripheral surface of thestationary member and between the neighboring bolt hole-providedprojecting pieces. Along therewith, since that another portion of thestrain sensor unit is fixed to the outer peripheral surface of thestationary member, the sensor unit for the load detection can beinstalled compactly in the automotive vehicle.

Since that portion of the strain sensor unit is fixed to the sensorfixing projecting piece, which is a dedicated component part, the straingenerating member of the strain sensor unit can be stably fixed to thestationary member. Accordingly, it is possible to suppress variation ofthe sensor output from the strain sensor unit and to stabilize it. Also,since the strain generating member is a simple component part that isprovided in the stationary member, fitting the strain sensor unit or thelike thereto is effective to render the mass productivity to beexcellent and to reduce the cost as compared with the conventional art,in which a strain gauge is bonded to an outer ring. Yet, as comparedwith the case in which that portion of the strain sensor is fixed to thebolt hole-provided projecting piece, there is no possibility ofinterference of the strain sensor unit with bolts or the like that arethreadingly engaged in the bolt hole-provided projecting piece and thefreedom of design can be increased correspondingly.

[Second Aspect of Fourth Mode]

In the first aspect of the fourth mode, of the outer peripheral surfaceof the stationary member, at a position which lies in the same phaserelative to a circumferential position of the sensor fixing projectingpiece, a pedestal projecting in a radially outward direction may beprovided, an upper surface of which is flattened to define a flat areato which that another portion of the strain sensor unit is fixed. Inthis case, that another portion of the strain sensor unit can be tightlyprovided in correspondence with the flattened surface of the flat area.Accordingly, unlike the case, in which it is fixed to an outerperipheral surface, which is a cylindrical surface, of the stationarymember of the wheel support bearing assembly, that another portion ofthe strain sensor unit can be firmly and stably fixed to the flat area.The work of fixing such another portion of the strain sensor unit iseffective to reduce the length of time required to complete such fixingwork and also to lessen the work load, as compared with the case inwhich the strain generating member is fixed to the generally cylindricalsurface.

[Third Aspect of Fourth Mode]

In the first aspect of the fourth mode, the fixing of the straingenerating member and the stationary member together may be carried outby the use of either one of a bolt and a bonding agent or the both orwelding.

If the strain generating member and the stationary member are fixedtogether by the use of any one of the foregoing methods, the straingenerating member can be firmly fixed to the stationary member. For thisreason, there is no possibility that the strain generating member maydisplace in position relative to the stationary member, and it istherefore possible to transmit the deformation of the stationary memberto the strain generating member accurately.

[Fourth Aspect of Fourth Mode]

In the first aspect of the fourth mode, the strain generating member maybe of an L-shaped configuration including a radially oriented portionextending in a radial direction and an axially oriented portionextending in an axial direction

[Fifth Aspect of Fourth Mode]

In the first aspect of the fourth mode, the strain generating memberreferred to above may be fitted to the outer peripheral surface of thestationary member and the sensor fixing projecting piece throughrespective mounting members. In this case, the strain generating membercan have a simplified shape and, accordingly, the processing of thestrain generating member can be facilitated with the cost reducedaccordingly.

[Sixth Aspect of Fourth Mode]

In the first aspect of the fourth mode, the stationary member can be theouter member. In this case, a portion of the strain sensor unit has tobe fitted to the sensor fixing projecting piece on the outer peripheralsurface of the outer member.

[Seventh Aspect of Fourth Mode]

In the first aspect of the fourth mode, an acting force calculatingsection may be provided, which is operable to calculate an externalforce acting on the wheel support bearing assembly or a force actingbetween a wheel tire and a road surface in response to an output formthe strain sensor unit.

As hereinbefore fully described, in each of the preferred embodiments ofthe present invention and the applied examples, reference has been madeto the outer member 1 serving as the stationary member, but the presentinvention can be equally applied to a wheel support bearing assembly ofa type, in which the inner member serves as the stationary member, inwhich case the strain sensor unit 21 is to be provided on a peripheralsurface which forms an inner periphery of the inner member 2.

Also, although each of the preferred embodiments of the presentinvention and the applied examples has been shown and described asapplied to the wheel support bearing assembly of the third generationtype, the present invention can be equally applied to a wheel supportbearing assembly of a first or second generation type, in a bearing unitand a hub comprises members separate from each other, and also to awheel support bearing assembly of a fourth generation type, in which aportion of the inner member is constituted by an outer ring of aconstant velocity joint. Also, this sensor equipped wheel supportbearing assembly is applicable to any wheel support bearing assembly foruse in supporting a vehicle driven wheel and, yet, to a tapered rollerbearing assembly of any of the various generation types for the supportof a vehicle wheel.

Although the present invention has been fully described in connectionwith the preferred embodiments thereof with reference to theaccompanying drawings which are used only for the purpose ofillustration, those skilled in the art will readily conceive numerouschanges and modifications within the framework of obviousness upon thereading of the specification herein presented of the present invention.Accordingly, such changes and modifications are, unless they depart fromthe scope of the present invention as delivered from the claims annexedhereto, to be construed as included therein.

1. A sensor equipped wheel support bearing assembly for supporting avehicle wheel rotatably relative to a vehicle body, which assemblycomprises: an outer member having an inner periphery formed with aplurality of rolling surfaces; an inner member having rolling surfacesdefined therein in face-to-face relation with the respective rollingsurfaces in the outer member; a plurality of rows of rolling elementsinterposed between those rolling surfaces; a strain sensor unit, made upof a strain generating member and a sensor element fitted to the straingenerating member for detecting strains induced in the strain generatingmember, is fitted to one of the outer and inner members, that serves asa stationary member; and a covering member that covers at least thesensor element sealingly, provided on a mounting surface of the straingenerating member of the strain sensor unit, on which the sensor elementis mounted, the covering member being made of a resin, which isover-molded, or an elastomer bonded by vulcanization.
 2. The sensorequipped wheel support bearing assembly as claimed in claim 1, whereinthe strain generating member includes first and second contact fixingelements fixed to respective locations of the stationary member, thefirst contact fixing element being fixed to a flange surface provided inthe stationary member and the second contact fixing element being fixedto a peripheral surface of the stationary member.
 3. The sensor equippedwheel support bearing assembly as claimed in claim 1, wherein the sensorelement in the strain sensor unit is provided with a cable drawnoutwardly from a location proximate to the second contact fixing elementin the strain generating member fixed to the peripheral surface of thestationary member in a direction circumferentially of the stationarymember.
 4. The sensor equipped wheel support bearing assembly as claimedin claim 3, wherein the cable is fixed to the peripheral surface of thestationary member by means of a clamp member equipped with a ferrite. 5.The sensor equipped wheel support bearing assembly as claimed in claim1, further comprising an acting force calculating section operable inresponse to an output from the sensor element to calculate an externalforce acting on the wheel support bearing assembly or a force actingbetween a tire and a road surface.
 6. The sensor equipped wheel supportbearing assembly as claimed in claim 1, wherein the strain generatingmember is of an L-shaped configuration including a radially orientedsegment, extending in a radial direction, and an axially orientedsegment extending in an axial direction.
 7. The sensor equipped wheelsupport bearing assembly as claimed in claim 1, wherein the straingenerating member of the strain sensor unit includes two or more fixingfaces adapted to be fixed to respective locations of the outer memberspaced from each other, and contact fixing elements each interposedbetween each of the fixing faces and a fixing target surface to whichthe strain sensor unit is to be fixed, the contact fixing element beingin the form of a spacer member having opposite end faces, one end faceoriented towards the fixing face having a shape conforming with that ofthe fixing face and the other end face oriented towards the fixingtarget surface having a shape conforming with that of the fixing targetsurface.
 8. The sensor equipped wheel support bearing assembly asclaimed in claim 7, wherein at least one of the two or more spacermembers is so designed that the end face oriented towards the fixingface is in the form of a flat face and the end face oriented towards thefixing target surface is in the form of a cylindrical surface.
 9. Thesensor equipped wheel support bearing assembly as claimed in claim 1,wherein one of the outer and inner members, that serves as thestationary member, is formed integrally with a sensor fixing boss, andthe strain generating member and at least one strain sensor unit fittedto the strain generating member are provided in the stationary memberthrough the sensor fixing boss.
 10. The sensor equipped wheel supportbearing assembly as claimed in claim 9, wherein the sensor fixing bossincludes a first boss formed integrally with the flange surface providedin the stationary member and a second boss formed integrally with theperipheral surface of the stationary member, and wherein the straingenerating member includes a first contact fixing element adapted to befixed to a foremost end face of the first boss in contact therewith anda second contact fixing element adapted to be fixed to a foremost endface of the second boss in contact therewith.